Unexpected Sources of Peanut Allergy

Attention new moms: Some lotions and creams for soothing scaly or irritated skin run the risk of triggering immune reactions in your infant that could lead to a serious food allergy months later. Or so conclude the authors of a new study in England.

Gideon Lack of St. Mary’s Hospital at Imperial College in London headed a team that followed almost 14,000 children from the womb through age 6. The researchers compared potential predisposing factors to peanut allergy in children who developed the sensitivity with those who didn’t.

Peanuts are one of the most common foods to trigger allergic responses. In the United States alone, some 1.5 million people have a demonstrated sensitivity to the proteins in this popular legume–and thus are at risk of developing life-threatening reactions. Indeed, those reactions claim the lives of some 50 to 100 people in the United States each year.

Individuals don’t develop allergies to peanuts or other triggering proteins upon their initial exposure. Susceptible people must first create antibodies to an offending protein, based on earlier encounters. Those early exposures don’t even require eating the food. Skin contact with peanut protein, for instance–perhaps through exposure to the small amounts in peanut oil–could, in vulnerable individuals, elicit the allergy-triggering antibodies.

That appears to be exactly what happened in most of the 49 children with peanut allergy in the new British study. Almost invariably, they developed a food allergy’s characteristic wheals, flushing, and hives after what appeared to be their first exposure to peanuts–usually by age 2. Further probing by the researchers uncovered that many of these children had skin contact with creams and oils containing anywhere from 0.3 to 100 percent peanut oil, according to a report in the March 13 New England Journal of Medicine.

Some of the emollients had been marketed as treatments for diaper rash, and a few were targeted to scaly scalps. In the new study, children whose skin had been exposed to such peanut-oil-laced products were 6.8 times as likely to develop peanut allergy as those exposed only to peanutfree products. Some mothers in the study had used creams containing peanut oil for soothing chapped breasts, but this exposure to peanut proteins didn’t seem to affect babies’ allergies.

The good news for U.S. parents is that the peanut-based baby and nursing products identified in this study aren’t sold in the United States, notes Anne Muoz-Furlong, founder of the nonprofit Food Allergy and Anaphylaxis Network, a national educational group with 25,000 members. Indeed, she says, “we did a study looking generally at creams for nursing mothers [and for babies with diaper rash] in the United States, and none of them contained peanut oil.”

However, many other cosmetics, body lotions, hydrating creams, and soaps do contain peanut oils, nut oils, and soy oils, Lack points out. “Although not directly prescribed for use on infant skin,” he notes, “it’s not uncommon for mothers to apply these products on their babies–because these preparations are marketed as benign and good for the skin.”

These skin-care products are available throughout the United States, Muoz-Furlong observes. “And all of them could potentially sensitize [babies to peanut allergy],” warns Lack, a pediatric allergist and immunologist.

The skinny on peanut allergy

Lack notes that parents tipped him off to the possible peanut problem posed by baby lotions. Several mentioned that their infants seemed to break out when they used the products–especially youngsters with eczema or other rashes.

That’s not surprising, he notes, since “skin inflammation tends to switch on allergic responses.”

“The fascinating thing,” Lack says, was the apparent lack of risk from babies’ oral exposure to breast creams containing peanut oil, several of which were quite popular in Britain at the time the study was under way. “Children who are suckling the breast would ingest these oils that mothers had been applying to their chapped nipples,” he observes, and would therefore seem to face an elevated risk of allergy. But his data showed there was the same rate of usage of these peanut-oil-containing creams in the mothers of children who did and didn’t develop peanut allergy. Moreover, mothers of children with peanut allergy hadn’t consumed more of the legumes during pregnancy or lactation than had other mothers.

A mom’s ingestion of peanut products makes no difference, Lack concludes. “Only when the peanut oil is applied to the infant’s skin does it seems to make a difference–and particularly if the skin was inflamed.”

Intuitively, he says, “that makes sense, because we’re not meant to become allergic to things that we eat.” From an evolutionary point of view, he says, exposure to foreign proteins through the gut should “lead to tolerance”–the dampening of an allergic response–”which indeed it does in the majority of individuals.”

The body doesn’t have the same protection against an allergic response to foreign proteins and other substances that don’t go through the gut. Indeed, Lack notes, people who work in the food industry and thereby breathe traces of food-derived proteins often acquire contact or inhalation allergies to those foods “while being able to still [safely] eat them.”

This suggests, he says, that “low-dose exposures through a route other than the gastrointestinal tract may actually switch on an allergy.” Higher exposures, he says, tend to switch on another part of the immune system, which correlates with the development of tolerance. In other words, exposures to tiny amounts of proteins, such as can contaminate peanut oil, “may in fact be more allergenic than high-dose exposures.”

Soy–a pseudo-peanut?

The new British study found that certain additional factors appeared to distinguish some of the children who developed peanut allergy. For instance, they were, as a group, 2.6 times as likely as the other youngsters to have a history of rash over joints and skin creases, and 5 times as likely to have experienced oozing, crusted rashes. Both symptoms may signal a heightened immune sensitivity.

Even more intriguing, Lack says, is the fact that children with peanut sensitivity were significantly more likely to have been fed a soy-based formula or milk. Overall, 8.3 percent of the infants had consumed such products. Among those with peanut allergy, the rate was 24.5 percent. Indeed, the researchers observe, “of the 10 children for whom data on the first consumption of soy milk or soy formula were available, 9 had consumed soy before reacting to peanuts.”

Soy, like peanuts, is a legume. The suspicion, Lack says, is that soy contains one or more proteins that the immune system confuses with their counterpart in peanuts. Such “cross-reactivity” is common. Touching a banana, for instance, can trigger hives in people allergic to latex and other rubber products. And in one particularly interesting case, a man allergic to poison ivy developed a marked reddening of the skin after peeling a mango (see https://www.sciencenews.org/sn_arc98/8_8_98/food.htm). The fruit’s skin contains chemicals, called oleoresins, that are akin to those in the leaves and roots of poison ivy.

Though Lack says that his team will be investigating the soy–peanut allergy connection carefully in months to come, “my own view is that even with soy, exposure through this skin route was the root [source of any cross-sensitization]. Remember, as infants eat, half of the food gets inside them and the rest splashes all over the skin.”

Need for constant vigilance

Having an allergy to peanuts is traumatic, Muoz-Furlong says, because victims live in fear of unwitting exposure to just a trace of the legume. Indeed, studies last year highlighted the risk posed by a mere peck on the cheek from someone who had recently eaten peanuts, even if they had brushed their teeth (see A Rash of Kisses).

A peanut-allergy vaccine, as described this week in the same issue of the New England Journal of Medicine that contains Lack’s study (see Tough Nut Is Cracked: Antibody treatment stifles peanut reactions), could lessen the threat posed by such chance exposures to peanut proteins. Although the vaccine tested in volunteers wouldn’t allow allergic individuals to down a package of the nuts, says Muoz-Furlong, it could give people with the disease “a little peace of mind” if they know that their next reaction will be manageable rather than potentially fatal.

However, even if the new vaccine reaches the market, the key to managing risk is remaining vigilant, Muoz-Furlong says. For instance, parents need to read product labels carefully.

Unfortunately, even that isn’t always enough. Lack observes that many of the peanut-oil creams and lotions noted in the British study identified the legume product as arachis oil. Arachis, derived from the Greek, is the name of the genus to which peanuts belong.

Moreover, notes Hugh Sampson of Mount Sinai Medical Center in New York, trace contamination of commercial products with peanut proteins is common. At a press conference in Denver this week, he noted that among companies making foods or other goods with peanuts or their derivatives, up to one-quarter of their other product lines may carry traces of peanut, which go unnoted on labels. This happens when equipment isn’t completely cleaned before use on peanutfree-product runs, or residues of the legume become airborne in a factory and settle onto supposedly peanutfree goods.

Back to the creams, soaps, and lotions: Lack cautions parents and caregivers to pay attention to their own hygiene. Even if they don’t put peanut-oil-containing products directly onto a baby, he warns “mothers with young infants who have rashes or a [family] history of allergy need to be cautious in using these creams on themselves and other members of their family.” Why? Peanut proteins can be transferred to a baby’s skin when a caregiver bathes a child or changes its diaper.

And in households with no history of the allergy? “It would be less of a problem–but not zero problem,” Lack says, “because we find children with peanut allergy being born into nonallergic families.”