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Origins of peanut allergy

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“I call a spade a spade.”

Robert Burton. The Anatomy of Melancholy (1621–51)

The use of straightforward language could prevent a lot of trouble. It seems bizarre, for instance, that when we use peanut oil medically we call it arachis oil so that many doctors and nurses, and almost all of the general public, must be unaware of what it is. Much has been written about the apparent increase in peanut allergy in recent decades but there is still a good deal of uncertainty about its origins. Now data from the Avon Longitudinal Study of Parents and Children (

) have pointed to the use of peanut oil skin preparations in young children as a possibly important factor.

From a cohort of 13 971 pre-school children born between April 1991 and December 1992, 49 were found to have a convincing history of peanut allergy. Thirty-six of these had skin testing and double blind, placebo controlled oral peanut challenge testing. Twenty-nine had positive skin reactions to peanut and 23 of those had positive challenge tests. The 49 children were compared with 70 atopic (eczema in mother and child) controls and 140 normal controls.

Specific IgE to peanuts was not detectable in saved cord blood from 23 children with peanut allergy and there was no significant correlation between peanut allergy and maternal peanut consumption in pregnancy. Transplacental sensitisation of the fetus therefore seemed unlikely. Likewise, sensitisation through breastfeeding was unlikely because peanut allergy was not significantly related to breastfeeding or to maternal peanut consumption during lactation; neither was there an association with the use of breast creams containing peanut oil.

Peanut allergy was, however, significantly associated with having been given soy milk or soy formula in the first 2 years of life and with eczematous rashes in infancy. The effect of soy could not be explained simply on the grounds of its use for allergic manifestations prior to the onset of peanut allergy. It is possible, but not proved, that cross-reacting allergens in soybeans might sensitise young children to peanuts.

Creams containing peanut oil were used very commonly for young infants: 59% of normal controls, 53% of atopic controls, 84% of children who developed peanut allergy, and 91% of children with a positive challenge test. They had been used as emollients for nappy rashes, eczema, dry skin, and other skin problems. The association with peanut allergy was not explained simply by the prevalence of skin problems in children who developed peanut allergy since children in the atopic control group were just as prone to skin problems but less likely to have had peanut oil creams applied. Creams not containing peanut oil had been used equally in the atopic control and peanut allergy groups. These researchers postulate that sensitisation occurs when peanut oil is applied to inflamed skin. The use of peanut oil cream increased the likelihood of peanut allergy sevenfold.

The use of peanut oil based emollient creams for young children is associated with increased risk of later peanut allergy. Soy milks might also increase the risk. At a time when there is so much anxiety about peanut allergy it seems strange, to put it mildly, that we are so busily applying peanut oil to the skin of young children. The mothers in this study did not know they were using peanut oil creams. Perhaps calling peanut oil peanut oil would be a good start.