A. Case study
B. More information
C. Editors' comments
E. CPD questions (South Africa, Australia)
A. Case study
A mother took her
2-year-old daughter to see the 4th doctor regarding her persistent eczema.
She had generalized eczema that did not have a specific pattern throughout
the day and was only partially controlled by medication. The clinical
history revealed that the child was exclusively breastfed from birth
and that solid foods were introduced at the age of 6 months. Within
a few weeks of this, the child developed a rash over her whole body.
This was diagnosed as eczema by a pediatrician, and topical creams were
prescribed. As she grew older, the eczema grew worse. She was placed
on more medication. At the time of the 4th consultation, she was on
2 types of antihistamine and 2 types of steroid cream. Her general practitioner
had done blood tests, but all serum-specific IgE levels were normal.
It was not known whether total IgE had been done. She was placed on
a low-allergenic diet with oral challenges, but this could not determine
any cause. The mother suspected that additives aggravated the eczema.
She began excluding these from her daughter's diet, and the symptoms
improved slightly. Now the child was eating mainly homemade foods and
few processed or pre-prepared foods. According to the mother, there
was no other apparent cause or aggravation of the persisting skin reaction.
Could additives be causing the eczema?
It is possible. The mother stated that the exclusion of additives from
her daughter's diet improved her condition. But it was clear that something
else contributed to the symptoms. What were the options for further
a. Question the mother about the family history of allergy.
b. Question the
mother about non-food factors in the child's environment (e.g., exposure
to house dust mite, pets, smoke, perfumes, fabric softeners) that could
aggravate her condition.
c. Investigate whether
the child was exposed to (and perhaps reacting to) additives that the
mother was not aware of. For example, the mother might consider sausage
to be free of additives, but in actual fact most sausages are not.
d. Redo blood tests,
or do skin prick tests.
e. Redo a low-allergenic
diet with oral challenges, or do an elimination diet.
a. The mother had light asthma, and the father hay fever; both to environmental
allergens. This constituted a family history of allergy, but there was
no known food allergy. The likelihood that the child had a food allergy
was therefore lower.
b. There was no
indication that any environmental factor had an effect on the child's
condition. The mother had already made some changes in the house environment.
c. A detailed diet
history was taken, but there were no indication that the child was ingesting
d. There was no
reason to redo the serum-specific IgE tests, as the results would not
have changed in such a short period of time-unless new allergens were
tested for. There was, however, no hint as to which allergens could
be relevant in this case. In some cases, it might be worth redoing serum-specific
IgE tests as the results may change over time (some patients may develop
tolerance to an allergen, while others may have been in the process
of developing an allergy when the original IgE test came up negative,
and still others may develop a totally new allergy). A total IgE test
would be helpful in determining whether the child had an IgE-mediated
reaction at all.
Can skin prick tests
be done on an eczema patient? Only if the patient's forearm is clear
of eczema. Otherwise, the skin could have a falsely positive reaction
because of its sensitivity. Also, the patient must have been off antihistamines
and steroid creams for a period of at least 7-10 days. If not, the test
results could be falsely negative, with the medication preventing an
immune response. The child's forearm was free of eczema at that time.
She was not using topical creams on that area but was on a low dose
The doctor decided
to do a skin prick test for potato. This decision was based on recent
evidence that potato is a more relevant allergen than was previously
thought. Children under a year of age can develop an allergy to potato,
as it is usually one of the first solids included in an infant's diet.
The child in question had first developed the reaction at the time of
the introduction of solids. The mother could not say that she had ever
noticed an association between her daughter eating potato and the aggravation
of her eczema. The child, however, enjoyed eating potato and ate it
on a regular basis. The skin prick test was done using fresh raw potato.
Within minutes, the child's arm started to itch. Not only did she react
to the skin prick test, but she also developed papules (solid elevated
lesion usually <10 mm) in the area of contact with potato (see picture
below). Potato was thus identified as a possible major contributing
factor in the eczema. The next step was to exclude this food from the
diet to see whether the symptoms improved.
and cooked) was excluded from the child's diet, and her symptoms
improved dramatically. The improvement was so great that she no
longer needed medication.
e. A low-allergenic
diet was to be the next step if the exclusion of potato did not
improve the child's symptoms. Even though it had been done before,
it was not certain that it had been done properly.
|TIP for Allergy
In the case of a patient with suspected potato allergy, the
Allergy Advisor database offers a quick reference to all the
information that could be helpful in the assessment and management
of such a patient: background information on potato (such
as its various uses, which track "hidden allergen"
and non-food exposure), the allergens that have been identified
in potato, symptoms of IgE-mediated and other types of reactions
to potato that have been reported in medical literature, possible
cross-reactions with other foods, a list of other foods that
belong to the same family as potato, and the references that
were used for the above information.
B. More information:
consumption of potato, allergy to potato is reported to be uncommon,
and allergy to potato pollen even more uncommon. But the condition is
probably underdiagnosed as we understand from recent literature.1
Adverse reactions to potato seem to be more prevalent in atopic individuals,
especially in birch pollen-sensitive individuals.2
Potato's biochemical composition includes proteins, glycoproteins and
alkaloids (including solanine).1 One study reported that potato flour
and starch are not allergenic.3 The study, however, did not
evaluate the heat-stability of potato allergens. This opinion should
therefore be reviewed, based on recent findings.
many proteins, consisting of amino acid sequences. Some of the sequences
(or whole proteins) are seen as hostile by the body, which mounts immune
responses against them. In other words, they are allergens. In potato,
only a few of the known allergens have as yet been characterised,3
namely Sol t 1, Sol t 2, Sol t 3.0101, Sol t 3.0102, and Sol t 4.4,5,6
Potato-allergic individuals may be allergic to all the allergens or
only to one or a few.
Cooked potato is
usually well tolerated. Adverse reactions to both raw and cooked potato,
however, have been documented.7 This is because both heat-labile
and heat-stable allergens can be present.7,8 Some people
can eat and handle cooked potatoes without adverse reactions, but not
raw potatoes.2 This difference would be due to the presence
of a heat-labile allergen.
Among the allergens
identified, most of the focus has been on Sol t 1 (also known as patatin).
It is reported to be a significant IgE-binding protein in children with
a positive skin-specific IgE to raw potato, and it appears to be a relevant
allergen in atopic dermatitis. There are conflicting reports on the
heat-stability of this allergen, but it has been found partially stable
Potato belongs to
the family Solanaceae. Other members of the family include tomato, cherry,
eggplant, melon, pear, paprika, bell pepper, cayenne pepper, red pepper,
tobacco, and chili.1 Cross-reactivity can be strong within
the same family, but there does not seem to be a strong cross-reactivity
within this family. Potato and tomato, however, both contain the allergen
patatin, and this may explain some of the cross-reactivity between these
foods. Patatin has not been found in other members of the family.
"similarity" in the amino acid sequences of the proteins.
The homology of an allergen in a plant (or animal) with another
allergen in another plant (or animal) is expressed as a percentage.
The higher the percentage, the more likely cross-reactivity will
occur between the items. Patatin has 60% homology with a patatin-like
allergen, Hev b 7, present in latex. In other words, the amino acid
sequences in patatin are 60% similar to the amino acid sequences
in Hev b 7.5,10 Patatin is thus a major cross-reactive
protein in latex-associated potato allergy and appears to be relevant
for atopic dermatitis. In other words, if a person reacts to patatin
(in potato) specifically, he or she may, because of cross-reactivity,
react to Hev b 7 (in latex) as well. But the cross-reactivity between
Hev b 7 and patatin appears to be restricted mainly to latex-sensitized
adults, suggesting a different mechanism of sensitization in children
with atopic dermatitis.9 More on sensitisation below.
other proteins that may cause adverse reactions, including the panallergen
profilin,11,12 and a chitinase (also a panallergen).13
Chitinase was identified as present in the potato plant, but its role
as an allergen in the potato tuber specifically has not been defined.
It is not even clear whether the chitinase is present in the tuber itself,
as opposed to other parts of the plant. Adverse reactions have been
reported to chitinase in other plants.
Reactions to potato can occur as a result of the ingestion of potato1,
the inhalation of finely dispersed particles of raw potato2,14
or the inhalation of the plant pollen.1 Skin reactions are
most often caused by handling potato, and other reactions by the ingestion
Reactions have been
reported to raw and cooked potatoes. As noted above, some people can
eat and handle cooked potatoes without adverse reactions, but not raw
The onset of allergic
reactions to potato differs among individuals.7 Immediate,
late and delayed reactions have been reported to both raw and cooked
potato.7,16 This may indicate that both IgE-mediated and
other activation pathways are involved.16
adverse reactions have been reported, including:
Gastrointestinal symptoms: nausea, vomiting, diarrhoea, abdominal
pain, itching of the mouth, laryngeal oedema, Oral Allergy Syndrome,
and pain in the throat.17,18
Cutaneous symptoms: urticaria, contact urticaria, urticaria,
angioedema, protein contact dermatitis, eczema, atopic dermatitis
and the exacerbation of atopic dermatitis.19
Respiratory symptoms: rhinoconjunctivitis, rhinitis, sneezing
and dyspnoea. One author found that potato is among the 6 foods
most frequently associated with childhood asthma (the others being
egg, milk, wheat, fish, and pork).20
Systemic symptoms: hypotension and food-dependent exercise-induced
anaphylaxis.21,22 There have been reports of children
developing anaphylaxis induced by raw14,23 and cooked
In adult patients
with pollen allergy, allergy to raw potato is associated mainly with
Oral Allergy Syndrome. These patients seem to react to an allergen present
in potato that is similar to an allergen in the pollen of birch, grass
There have been
many reports of adverse reactions in adults handling or peeling raw
potatoes. Most reports were of housewives and workers in the potato
industry (i.e., occupational allergy). Symptoms reported include rhinoconjunctivitis,
asthma, contact urticaria, atopic dermatitis, angioedema and immediate
finger itching upon handling raw potato.2,6,14,24,25,26,27But
there have also been reports of children with reactions, ranging from
contact urticaria15,19 to anaphylaxis,14,23 due
to contact with raw potato.
How does sensitization
The literature has shown both primary and secondary sensitization to
a. Primary sensitization:
In children, as discussed above, sensitization is probably not latex-associated.
White potato is a very common ingredient in the diet of Western countries,
and in its cooked form it is one of the first solid foods introduced
into a child's diet, usually around the age of 4-6 months.16
Because there are reports of children of less than a year of age developing
adverse reactions to cooked potatoes,28 it is proposed that
sensitization can occur this early.
occur early in life but present with symptoms only later. Also, the
symptoms that a person presents with can worsen with time. There was
a case of an 11-year-old girl, exclusively breast-fed for her first
4 months, who developed anaphylactic symptoms after ingestion of cooked
potato at 5 months of age, when she was fed potato for the first time.
Subsequently, she developed urticaria, angioedema, and respiratory and
systemic symptoms on contact with potatoes, ingestion of potatoes, and
exposure to cooking potatoes or potato pollen.1
It is proposed that, in some adults, initial sensitization to potato
occurs by exposure to latex. Thereafter, Hev b 7-specific antibodies
detect homologous regions in potato patatin to mediate potato allergy.
It is suggested that the molecular basis of atopic dermatitis and acquired
latex-fruit syndrome are different and should be carefully compared.9
interesting example of secondary sensitization via primary sensitization
was reported: A woman experienced adverse reactions to potato, tomato
and latex. She worked with raw potatoes and tomatoes for years,
without any adverse effects, until she started wearing rubber gloves.
It may be that her allergy to latex arose secondarily via primary
sensitization to potato and tomato.10
- Cooked potato
can be dried and made into a powder and used as a thickener, or it
can be added to cereal flours that are ingredients of bread, cookies,
- Potatoes may
be used for medicinal purposes:
- The leaves are
said to be antispasmodic.
- A juice made
from the tubers is used to treat peptic ulcers. But excessive doses
potato juice can be toxic.
- Raw and cooked
potatoes have many functions as topical applications, e.g., for
rheumatic joints, swellings, skin rashes, haemorrhoids, burns, scalds,
If a person reacts
to contact with potato, there are possible non-food exposures he or she
should be aware of. For example:
- The potato is
a source of starch for sizing cotton and making industrial alcohol,
and for many other purposes in industry.
- Ripe potato juice
is an excellent cleaner of silks, cottons and woolens. The water in
which potatoes have been boiled can be used to clean silver and to
restore a shine to furniture.
- Emollient and
cleansing facemasks are made from potatoes and used to treat hard,
greasy and wrinkled skin.
Skinned Potatoes or pre-cut French fries may be dipped in a sulphite
or metabisulphite solution to prevent browning. The sulphite may trigger
asthma in susceptible individuals.29,30
b. Solanine (also
known as Solasonine or Solanidine):
Solanine is a glycoalkaloid and a naturally occurring toxicant in plants
that are members of the Solanaceae family. Solanine is present at low
levels in the great majority of commercial varieties of potatoes and
tomatoes available, but the substance can accumulate to high levels
in greened (with green skin from exposure to light), stored or damaged
potatoes. If ingested in large amounts, solanine may cause poisoning
in humans and farm animals. Acute poisoning, including gastro-intestinal
and neurological disturbances, may occur. Most individuals have a low
serum level of solanine at any point in time and, according to the World
Health Organization, the normal level of solanine in potatoes, 20-100
mg per kg of potatoes, is not of toxicological concern.31,32
||compiled by Karen du Plessis
Food & Allergy Consulting & Testing Services (FACTS)
PO Box 565
Comments by our editors
Potato is one of the foods that are included in the few foods
diet as it is generally thought to be a low allergenic food. But
recent literature indicates that allergy to potato is not as uncommon
as originally thought. If a patient does not improve on a "low
allergenic" or few foods diet, one needs to consider that
the patient is reacting to one or more of the foods in this diet.
Apart from potato, the patient might be reacting to some of the
fruit in the diet, which contain the panallergen, lipid transfer
For more information
on this subject and other allergy and intolerance related topics, visit:
To join a professional
food allergy discussion list where this subject can be discussed further,
go to http://groups.yahoo.com/group/AllergyDietitian
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" as the subject.
1. Castells, MC,
Pascual, C, Estaban, M, Ojeda, JA. Allergy to white potato. J Allergy
Clin Immunol 1986;78:1110-1114.
2. Quirce S, Diet Gomez ML, Hinjosa M, Cuevas, et al. Housewives with
raw potato-induced bronchial asthma. Allergy 1989;44:532-536
3. R. Wahl, Susanne Lau, et al. IgE-mediated Allergic Reactions to Potatoes.
Int Arch Allergy Appl Immunol 1990:92:168-174.
4. Seppala U, Majamaa H, Turjanmaa K, Helin J, Reunala T, Kalkkinen
N, Palosuo T. Identification of four novel potato (Solanum tuberosum)
allergens belonging to the family of soybean trypsin inhibitors. Allergy
5. Seppala U et al. IgE reactivity to patatin-like latex allergen, Hev
b 7, and to patatin of potato tuber, Sol t 1, in adults and children
allergic to natural rubber latex. Allergy 2000;55:266-73.
6. Seppala U, Alenius H, Turjanmaa K, Reunala T, Palosuo T, Kalkkinen
N. Identification of patatin as a novel allergen for children with positive
skin prick test responses to raw Potato. J Allergy Clin Immunol 1999;103(1
7. Majamaa H, Seppala U, Palosuo T, Turjanmaa K, Kalkkinen N, Reunala
T. Positive skin and oral challenge responses to potato and occurrence
of immunoglobulin E antibodies to patatin (Sol t 1) in infants with
atopic dermatitis. Pediatr Allergy Immunol 2001 Oct;12(5):283-8.
8. Iliev D, Wuthrich B. Occupational protein contact dermatitis with
type I allergy to different kinds of meat and vegetables. Int Arch Occup
Environ Health 1998 Jun;71(4):289-92.
9. Schmidt MH, Raulf-Heimsoth M, Posch A. Evaluation of patatin as a
major cross-reactive allergen in latex-induced potato allergy. Ann Allergy
Asthma Immunol 2002 Dec;89(6):613-8.
10. Tavadia S, Morton CA, Forsyth A. Latex, potato and tomato allergy
in a restaurateur. Contact dermatitis 2002:47:109.
11. Ebner C, Hirschwehr R, Bauer L, Breiteneder H, Valenta R, Ebner
H, Kraft D, Scheiner O. Identification of allergens in fruits and vegetables:
IgE cross-reactivities with the important birch pollen allergens Bet
v 1 and Bet v 2 (birch profilin). J Allergy Clin Immunol 1995;95(5 Pt
12. van Ree R, Voitenko V, et al. Profilin is a cross-reactive allergen
in pollen and vegetable foods. Int Arch Allergy Immunol 1992;98(2):97-104.
13. Verburg JG, Smith CE, Lisek CA, Huynh QK. Identification of an essential
tyrosine residue in the catalytic site of a chitinase isolated from
Zea mays that is selectively modified during inactivation with 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide.
J Biol Chem 1992;267(6):3886-93.
14. Nater JP, Zwartz JA. Atopic allergic reactions due to raw potato.
J Allergy 1967 Oct;40(4):202-6.
15. Delgado J, Castillo R, Quiralte J, Blanco C, Carrillo T. Contact
urticaria in a child from raw Potato. Contact Dermatitis 1996;35(3):179-80
16. De Swert LF, Cadot P, Ceuppens JL. Allergy to cooked white potatoes
in infants and young children: A cause of severe, chronic allergic disease.
J Allergy Clin Immunol 2002 Sep;110(3):524-35.
17. Ortolani C, Ispano M, Pastorello E, Bigi A, et al. The Oral Allergy
Syndrome. Ann Allergy 1988;61:47-52
18. Ortolani C, Ispano M, Pastorello EA, Ansoloni R, et al. Comparison
of results of skin prick tests (with fresh foods and RAST in 100 patients
with oral allergy syndrome. J Allergy Clin Immunol 1989;83:683-690
19. Meynadier J, Meynadier JM, Guilhou JJ. [Contact urticaria in atopic
patients. Apropos of 2 cases] Ann Dermatol Venereol 1982;109(10):871-4.
[Article in French]
20. Sabbah A. Food allergy in childhood asthma [French]. Allerg Immunol
21. Caffarelli C, Cataldi R, Giordano S, Cavagni G. Anaphylaxis induced
by exercise and related to multiple food intake. Allergy Asthma Proc
22. Caffarelli C, Giovanni C, Giordano S, et al. Reduced pulmonary function
in multiple food-induced, exercise-related episodes of anaphylaxis.
J Allergy Clin Immunol 1996;98:762-765
23. Beausoleil JL, Spergel JM, Pawlowski NA. Anaphylaxis to raw potato.
Ann Allergy Asthma Immunol 2001;86(1):68-70.
24. Jeannet-Peter N, Piletta-Zanin PA, Hauser C. Facial dermatitis,
contact urticaria, rhinoconjunctivitis, and asthma induced by potato.
Am J Contact Dermat 1999 Mar;10(1):40-2.
25. Larko O, Lindstedt G, Lundberg PA, Mobacken H. Biochemical and clinical
studies in a case of contact urticaria to potato. Contact Dermatitis
26. Gomez Torrijos E, Galindo PA, Borja J, Feo F, Garcia Rodriguez R,
Mur P. Allergic contact urticaria from raw Potato. J Investig Allergol
Clin Immunol 2001;11(2):129
27. Peter JN, et al. Contact urticaria from potatoes. Contact Dermatitis
28. Hannuksela M, Lahti A. Immediate reactions to fruits and vegetables.
Contact Dermatitis 1977;3(2):79-84
29. Taylor SL, Bush RK, Selner JC, Nordlee JA, Wiener MB, Holden K,
Koepke JW, Busse WW. Sensitivity to sulfited foods among sulfite-sensitive
subjects with asthma. J Allergy Clin Immunol 1988;81(6):1159-67
30. Steinman HA, Le Roux M, Potter PC. The incidence of Sulfite sensitivity
in South African asthmatic children. SAMJ 1993;83:387-390
31. Badowski P, Urbanek-Karlowska B. Solanine and chaconine: occurrence,
properties, methods for determination. [Polish] Rocz Panstw Zakl Hig
32. Harvey MH, Morris BA, McMillan M, Marks V. Measurement of potato
steroidal alkaloids in human serum and saliva by radioimmunoassay. Hum
Questions (South Africa, Australia)
ALL THE QUESTIONS
(There is only
one correct answer per question.)
1. Which of the following is not true regarding allergy to potato?
(a.) Some individuals react to only raw potato but not to cooked.
(b.) Some individuals react to only cooked potato but not to raw.
(c.) Some individuals react to both raw and cooked potato.
2. Which of the
following is not true regarding the potato allergen, Patatin?
(a.) It is also known as Sol t 1.
(b.) It appears to be a relevant allergen in atopic dermatitis.
(c.) It is not clear whether it is present in the potato tuber.
(d.) It is a major cross-reactive protein in latex-associated potato
3. Which of the
following is not a potato allergen, i.e., does not cause an allergic
(a.) The panallergen profilin
(c.) Sol t 2
4. Choose the correct
answer: Reactions to potato can occur as a result of:
(a.) The ingestion of potato
(b.) The handling of potato
(c.) The inhalation of the plant pollen
(d.) All of the above
5. True or false:
The onset of allergic reactions to potato can be immediate, late or
6. Which of the
following is not an example of proposed sensitisation to potato in potato
(a.) When potato is given as one of the first solid foods introduced
in the child's diet, usually around the age of 4-6 months.
(b.) Initial exposure and allergy to latex, leading to the development
of an allergy to potato thereafter.
(c.) Prolonged exposure to potato by handling the raw product in the
work situation (food industry).
(d.) Initial allergy to potato and tomato lead to sensitisation to latex
7. True or false:
Sulphite sensitive individuals may react to commercial pre-skinned potatoes
or pre-cut French fries.
8. Which of the
following is not true regarding solanine in potatoes:
(a.) It occurs naturally in members of the Solanaceae family.
(b.) It is usually present at low levels that are not of toxicological
(c.) It can accumulate to high levels when the potato is cooked.
(d.) Symptoms to solanine include gastrointestinal and neurological
|1. a [ ] b [X] c [ ]
||2. a [ ] b [ ] c [X] d
||3. a [ ] b [X] c [ ] d
|4. a [ ] b [ ] c [ ] d
||5. a [X] b [ ]
||6. a [ ] b [ ] c [ ] d
|7. a [X] b [ ]
||8. a [ ] b [ ] c [X] d
1. b. Some individuals
react to only cooked potato but not to raw.
2. c. It is not clear whether it is present in the potato tuber.
3. b. Solanine
4. d. All of the above
5. a. True
6. d. Initial allergy to potato and tomato lead to sensitisation to
7. a. True
8. c. It can accumulate to high levels when the potato is cooked.