Q:

An 8 year old girl came in with an acute urticarial eruption following touching a snake during a presentation at school. It occurred immediately upon touching the snake - first occurred on the hand she used to touch the snake, then spread to her arm, neck, face and chest. She had no associated symptoms. The only other animal presented during the session at school was an iguana. She responded well to Benadryl.

 

I thought snake and other reptiles are supposed to be "hypoallergenic?" What could she have reacted to? Should I advise against contact with reptiles in the future?

A:

Thank you for your recent inquiry.

From the history you described, it certainly appears as if the child had an acute urticarial reaction to contact with the snake. Therefore, you cannot rule out a possible allergy to reptiles, and snakes in particular.

Actually, allergic reactions to reptiles of various sorts have been reported in the literature in the past. These have occurred in particular to iguanas (see first two abstracts copied below).

In addition, there have been numerous reports of anaphylactic reactions to the venom of snakes (see third abstract copied below). Also, on the message boards in the lay material on the Internet, there are several anecdotal reports of respiratory allergy upon exposure to snakes.

Therefore it is not farfetched to think that reactions to contact with snakes are also possible.

I think that you would have to, therefore, accept the snake as the probable cause of her reaction. Thus it would be prudent for you to suggest avoidance of contact with reptiles. If, however, you wanted to pursue this further, I see no reason why you could not, following the example in the abstract below from the Journal of Allergy and Immunology, perform a prick test to a extract made from the scales of the snake if you felt the need to further document the snake as the culprit.

Unfortunately, I am not aware of, nor could I find with an Internet search, any manufactured allergens using reptile epidermal tissue.

Thank you again for your inquiry and we hope this response is helpful to you.

Three Abstracts:
The Journal of Allergy and Clinical Immunology
Volume 106, Issue 2 , Pages 369-372, August 2000 Abstract Background: Furry animals produce allergens that can cause allergic rhinitis and asthma. In contrast, scaly animals, such as lizards, are assumed not to be allergenic. Objective: We sought to evaluate a 32-year-old man who complained of allergic rhinitis and asthma symptoms that occurred exclusively in his own home. He had dogs and cats at home but denied any increase in symptoms specifically associated with these pets. Skin prick testing initially performed to 42 common aeroallergens, including cat, dog, and house dust mite, elicited negative results. He later reported that the symptoms were worse on exposure to his pet iguanas. Methods: Skin prick tests were subsequently performed to an extract made from scales from his pet iguana. Extracts were also prepared from several zoo reptiles. Immunoassays for IgE antibody, as well as IgE immunoblots, were performed by using these extracts and the patient's serum. Results: The skin prick test result with the pet iguana scale extract was positive. The patient's serum contained IgE antibody to his own pet iguana and to a zoo iguana. Conclusion: Our patient's history, skin test results, and in vitro studies clearly demonstrate that he is allergic to iguana. Physicians should be aware that such allergy to scaly pets may occur and should not restrict history taking to questions about furry pets. (J Allergy Clin Immunol 2000;106:369-72.)

Abstract
Although furry animals are known sources of respiratory allergy, scaly animals are assumed not to be allergenic. Exotic animals such as iguanas are becoming increasingly common pets. Nevertheless, these animals are not suspected to be allergenic. We present the case of a 42-year-old woman suffering from allergic rhinoconjunctivitis and asthma caused by a pet iguana. Clear IgE-sensitization and respiratory allergy to iguana scales is demonstrated, suggesting that scaly pets should be taken into account as possible allergenic sources.
J Investig Allergol Clin Immunol 2006; Vol. 16(3): 212-213

Abstract
A 55-year-old herpetologist developed rhinitis, asthma, urticaria and anaphylaxis when handling 4 different viper snake venoms. Allergen characterizations were done using SDS-PAGE, IgE immunoblotting and IgE inhibition experiments. The most prominent immunoreactive proteins were analyzed by MALDI-TOF mass spectrometry, and peptide identity was demonstrated by homology with known peptide sequences. SDS-PAGE showed several protein bands ranging from 5 to 99 kDa in each of the 4 snake venoms. Immunoblotting demonstrated 4 IgE-binding bands in the Bothrops extract of about 60, 28, 14 and 7 kDa. The bands of 28 and 14 kDa were also present in Lachesis muta. Two IgE-binding proteins of about 50 and 35 kDa were found in Bothrops atrox and L. muta, respectively. A strong inhibition of IgE binding to immobilize Bothrops asper proteins was observed after preabsorption of sera with B. asper, B. atrox,Bothrops xanthograma and L. muta extracts. MALDI-TOF analysis showed a 14-kDa phospholipase and the 60- and 28-kDa proteins showed significant similarity with metalloproteinases. In this report we have characterized the snake venom allergens that can elicit IgE-mediated symptoms.
Int Arch Allergy Immunol 2009;150:307-310 (DOI: 10.1159/000222684)

Sincerely,
Phil Lieberman, M.D.

AAAAI - American Academy of Allergy Asthma & Immunology