Does heredity determine the allergy manifestation or the sensitisation to a specific allergen?

The role of genetics in allergy development is well accepted. However, studies could not delineate the mode of inheritance or what is specifically being inherited. The purpose of this study was to determine the effect of genetics on the development of allergy manifestation, serum IgE level, and sensitization to specific allergens.

Fifty-eight twin sets (age 7 months to 11 years) were evaluated for allergy by medical history, family history, physical examination, serum total IgE level, and percutaneous testing to selected common allergens.

In 25 monozygotic (MZ) sets, concordance of atopy was significantly higher than in 33 dizygotic (DZ) sets (84.6% vs 62.5%). The age at onset tended to be earlier when the mother was allergic than when the father was (23.5 months vs 30.5 months). When both twins were allergic, the intra-pair difference in age at onset was within <6 months in 50% of MZ sets versus 31.8% in DZ sets. Total IgE level in twins showed a very strong correlation in MZ sets (r 0.92), but only a moderate correlation among DZ sets (r 0.57). Skin test positivity to specific allergens did not show a significant concordance between twins in either group.

Our study indicates that the genetic influence was strongest on the inheritance of IgE phenotype, the development of the atopic tendency, the age of onset, and to some extent on the specific allergy manifestation. The effect seemed less on determining the specific offending allergen(s), suggesting possible roles of epigenetic and environmental factors.