In allergy, cross reactivity is fairly common. An allergy to birch tree pollen may signal an allergy to apples; an allergy to bananas can indicate an allergy to latex. These are examples of different sources of proteins, but chemically they are similar. The chemical similarity can cause the body’s defense system to read them as one. Cross-reactivity is common in dust mite and storage mite allergens. Other examples of possible cross-reactive allergens are bird feathers and egg yolks, shrimp and mites, or grass pollen, with wheat or rye flour.(1) It has been known for some time that allergens of the house dust mite (European and American) cross-react with allergens of storage mites. House dust mites have evolved to live on discarded skin scales, mould and general organic debris, while its close relative, the storage mite can be found in barns, stored grains and mouldy environments. The storage mite, living mainly on plants, moulds and micro-organisms, is a vegetarian in comparison with the skin-eating house dust mite. (2,3) In spite of their different diets both mites, just like humans, have to break down digested fats in order to absorb nutrients. (4) The house dust mite has evolved to digest animal fats while the storage mite digests fat from plants. Although these mites have different diets, they share the same enzymes to dissolve fats in food. Sadly, for some of us, these shared enzymes are among the allergens that cause allergic reactions. The lesson here is important. People who are allergic to house dust mites may also be allergic to storage mites commonly found living in poorly stored grain. Some scientists prefer to call all these mites ‘domestic mites’ as they can be found in our homes and work places if the conditions are right.
Cross-reactivity between mites can be both subtle and dramatic. An example of an extreme reaction has been described in a legal medical journal published in 2003. (5) In the article investigators puzzled over the sudden and unexpected death of a farmer with symptoms of anaphylactic shock whose only allergy was to mites. They had to consider cross-reactivity with storage mites, house dust mite and shrimps as a possible cause of death. The 47 year-old farmer had a history of nocturnal allergic reactions and slept in a bed infested with house dust mites.(5)
Man has been cohabiting with mites for around 10,000 years. They are important as scavengers, but we must not encourage them to breed out of control in our homes or work places. Colonies of domestic mites can be controlled by limiting their food source and lowering humidity. In homes, stored grains should be kept in sealed bags or in the freezer.(6)
For further reading see Time Line 1995 (11)
References: References:
1. Ortolani C. et al. ´Diagnostic problems due to cross-reactions in food allergy´, Allergy’ 1998, 53, Suppl 46, pages 58 to 61
2. Feather IH, Warner JA, Holgate ST, Thompson PJ, Stewart GA. ´Cohabiting with domestic mites´, Thorax, 1993 48:5-9
3. Warner A, Bostrom S, Moller C, Kjellman N.I.M, ´Mite fauna in homes and sensitivity to house dust mite and storage mite: Allergy, 1999, 54, 681-690
4. Nigel Plummer PhD, Dietary Fats and Fatty Acids in Human Healthcare. BioMed Publications Ltd. 16 Oak Grove, Harborne, B32 2HR, England
5. Edston E, van Hage-Hamsten M, ‘Death in anaphylaxis in a man with house dust mite allergy’, Int. Journal Legal Med., 2003, Vol.117, pages 299 to 301
6. Colloff M,´Differences between the allergen repertoires of house-dust mites and stored-product mites´, Journal of Clinincal Immunoassay Vol.16, No.2, 1993
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