PEANUT: Loss of the positive skin test.

First seen at 6 months of age.

Was seen initially as an infant with eczema and at age two he reacted to peanut with swelling of an eye but no respiratory symptoms. He was found to have moderate positive skin tests to two preparations of peanut (7x7mmm and 6x5mm). He was negative to everything else. Shortly after that visit, while being fed in a restaurant, he developed soreness of the tongue and throat with heavy breathing and became sleepy. He vomited. He had no hives but had not been sick prior to eating at the restaurant. Since then he has avoided peanut and all nuts with no further reactions. He has no problem with fish or seeds, although he doesn’t like seeds. His eczema has improved and he has no other symptoms of allergy or asthma He does not seem to develop symptoms around his pet dog.

FAMILY HISTORY: No asthma or allergy in the immediate family but paternal grandfather has both.

ENVIRONMENTAL HISTORY: No one smokes in the home. There is a pet dog. Dust mite control is being done in the bedroom. No contact with mold, cockroach, mice or feathers.

PAST HEALTH: Unremarkable.

PHYSICAL EXAMINATION: Height: 116cms. Weight: 22kg. Examination of head and neck was unremarkable. Chest was clear to auscultation and the rest of the examination was normal.

SKIN TESTS: Negative to everything including two preparations of peanut and a series of nuts. Histamine control was positive.

PULMONARY FUNCTION TESTING: Fev1 was 0.98 or 80% predicted. The test was within normal limits.

Non-Atopic at present: He is among the happy few peanut sensitive patients who lose the positive skin test to peanut. In order to confirm the loss of IgE antibody, a CAP-RAST to peanut was ordered and was <0.35 KU/L, that is, below the level of detectibility of the test. This case history is similar to those I described in a study of children who lost the skin test reactivity to peanut (Go to article). Although he could have gone in either direction. He seems to have gone in the direction of minimal atopy. A peripheral blood eosinophil count was 0.2x E9/L and a serum IgE was 77 mcg/L (normal 0 - 150). He is not very atopic and chances are very good he will never have a recurrence of the IgE antibody to peanut.

First seen at 20 months of age.

At age 4, he put a Ritz peanut butter cookie in his mouth but spit it out without swallowing. He had no reaction.

A few weeks before his recent assessment, he bit into a chocolate covered peanut candy and then spit it out. He did not swallow it and had no reaction. He has had no reactions to other foods and avoids nuts as well as peanut. He eats fish without problem but has never had shellfish. He has no problems with seeds. With colds, he can cough and wheeze. At that time he is treated with Flovent and Ventolin. Between colds, he is free of asthma symptoms and off the puffers. His asthma has improved significantly in the last few years and he rarely needs puffers.

FAMILY HISTORY: No asthma but father is allergic.

ENVIRONMENTAL HISTORY: Father smokes outside the home. There are no pets. Dust mite control is being done in the bedroom. No contact with mold, cockroach, mice or feathers.

PAST HEALTH: Unremarkable.

PHYSICAL EXAMINATION: Height: 121cms. Weight: 26.2kg. Examination of head and neck was unremarkable. Chest was clear to auscultation and the rest of the examination was normal.

SKIN TESTS: Negative to everything including two preparations of peanut and a series of nuts. Histamine control was positive.

PULMONARY FUNCTION TESTING: Fev1 was 1.12 or 80% predicted. The test was within normal limits.

Non-Atopic at present: He has lost the positive skin test to peanut and is negative to nuts. He is negative to all other allergens including egg and all aeroallergens. It seems likely that his asthma has improved as he has gotten older because he has not become sensitized to aeroallergens and is develoiping fewer viral illnesses. In order to confirm the loss of IgE antibody, a CAP-RAST to peanut was ordered and was <0.35 KU/L, that is, below the level of detectibility. The total IgE was 150 mcg/L (normal 0-432) and peripheral eosinophil count was low at 0.2 x E9/L. At the time of his first visit, his positive skin tests to peanut were roughly the size described in children in the study who lost the skin test reactivity (Go to article). However I have seen many other children who at the first visit had only a small positive skin test to peanut but went on to develop a much larger positive and many other positive aeroallergen skin tests at follow-up. It is not possible to predict which child will lose the positive skin test to peanut when they are seen at the first visit. If at the first visit the child has many positive skin tests apart from peanut, I would be pessimistic about their chance of losing the positive skin test to peanut over time, although they might lose clinical reactivity. That can only be determined by an oral challenge with peanut done in an appropriate unit.

First seen at 6 months of age.

At 4 months of age she developed hives after being fed cow milk formula. On another occasion when her mother was eating peanut butter and touched her, she developed hives where she was touched. Skin testing at 6 months of age showed positive to milk (4 x 3mm) and also two solutions of peanut antigen (6 x 4 mm). The family had pet cats and she was negative on testing to the cats. Since that time she has come to tolerate dairy but has avoided peanut and nuts. She has had no reactions to any foods. The cats have remained in the home and she shows no signs of symptoms around the cats. She has had no signs to suggest asthma. She has no other symptoms of allergy.

FAMILY HISTORY: No asthma or allergy.

ENVIRONMENTAL HISTORY: No one smokes in the home. There are pet cats. Dust mite control is not being done completely in the bedroom.

PAST HEALTH: Unremarkable.

PHYSICAL EXAMINATION: Height: 104cms. Weight: 16.5kg. Examination of head and neck was unremarkable. Chest was clear to auscultation and the rest of the examination was normal.

SKIN TESTS: Borderline positive to two preparations of peanut (2 x 2 mm) but negative to a series of nuts and negative to all other allergens.

Mildly Atopic: The patient is losing the sensitivity to peanut and does not seem to be very atopic. She has not developed sensitivity to cat or other airborne allergens. That again is a good indicator that her immune system is not very committed to being atopic. She seems to fit very nicely into the group of patients that have lost their sensitivity to peanut although she still has a borderline positive skin test to peanut. This outcome was not predictable at her initial visit. A RAST test was done and proved to be <0.35KU/L to peanut with a total IgE of 59 (normal 0-60mcg/L) and a peripheral eosinophil count of 0.01 X E9/L (normal 0.02-0.5). Because of the borderline positives to peanut on skin testing, I would not perform an oral challenge in the office. Sampson has reported positive oral challenges with negative RAST tests and slightly positive skin tests to peanut. She was negative to nuts and in the home can have nuts. For the moment she will continue to carry the Epi-pen. In another few years she will probably lose all of the sensitivity to peanut but mother would like to have a challenge done now. That can only be done in a specialized unit since she continues to have small positives. She will be referred to the Hospital For Sick Children in Toronto for the challenge. Oral challenges are being done at Montreal Children's Hospital, Montreal Quebec; The National Jewish Hospital in Denver Colorado; Johns Hopkins University Hospital in Baltimore and The Mount Sinai in New York City to name a few.