Tagged Allergies

Thumb Suckers and Nail Biters May Develop Fewer Allergies

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Credit Getty Images

Babies have been seen sucking on their fingers in utero weeks before birth. But the sight of an older child with his fingers constantly in his mouth, sucking her thumb, biting his nails, can drive parents crazy, bringing up fears about everything from social stigma to germs.

A new study suggests that those habits in children ages 5 to 11 may indeed increase exposure to microbes, but that that may not be all bad.

When a pediatrician discusses thumb-sucking, it’s usually because a parent is worried. The thumb is in the mouth so constantly that there’s a worry about speech or about whether the teeth may be affected. It’s gone on too long, and an older child is being teased about it. And in those situations, especially when a child is over 4, we work with parents and children on how to break the habit.

Nail biting worries parents for similar reasons, and we often end up giving similar advice: Don’t make negative comments; look for the situations that bring on the behavior and find alternate strategies; praise and reward the child for not doing it; put a glove or a bandage on the hand to remind the child.

In a study published Monday in the journal Pediatrics, researchers drew evidence from an ongoing study of New Zealand children to show those whose parents described them as thumb-suckers and nail-biters were less likely to have positive allergic skin tests later in life.

The children were in the Dunedin Multidisciplinary Health and Development Study, in which 1,037 children born in 1972-73 in Dunedin, a coastal city in New Zealand, were assessed and tested as they grew up, with the most recent assessment done at age 38. Stephanie Lynch, a student at Dunedin School of Medicine and the first author of the paper, had the idea of using the data to look at a possible relationship between children who tend to have their fingers in their mouths and allergic sensitization.

The question of such a connection arose because of the so-called hygiene hypothesis, an idea originally formulated in 1989, that there may be a link between atopic disease — the revved-up action of the immune system responsible for eczema, asthma and allergy — and a lack of exposure to various microbes early in life. Some exposure to germs, the argument goes, may help program a child’s immune system to fight disease, rather than develop allergies.

In the study, parents were asked about their children’s nail-biting and thumb-sucking habits when the children were 5, 7, 9 and 11 years old. Skin testing for allergic sensitization to a range of common allergens including dust mites, grass, cats, dogs, horses and common molds was done when the children were 13 years old, and then later when they were 32. Thirty-one percent of the children were described as “frequent” nail biters or thumb suckers (or both) at one or more of those ages.

The study found that children who frequently sucked a thumb or bit their nails were significantly less likely to have positive allergic skin tests both at 13 and again at 32. Children with both habits were even less likely to have a positive skin test than those with only one of the habits.

These differences could not be explained by other factors that are associated with allergic risk. The researchers controlled for pets, parents with allergies, breast-feeding, socioeconomic status and more. But though the former thumb-suckers and nail-biters were less likely to show allergic sensitization, there was no significant difference in their likelihood of having asthma or hay fever.

Robert J. Hancox, one of the authors of the study, is an associate professor in the Department of Preventive and Social Medicine at Dunedin School of Medicine, a department that is particularly oriented toward the study of diseases’ causes and risk factors. He said in an email, “The hygiene hypothesis is interesting because it suggests that lifestyle factors may be responsible for the rise in allergic diseases in recent decades. Obviously hygiene has very many benefits, but perhaps this is a downside. The hygiene hypothesis is still unproven and controversial, but this is another piece of evidence that it could be true.”

Malcolm Sears, one of the authors of the paper, a professor of medicine at McMaster University in Hamilton, Ontario, who was the original leader for the asthma allergy component of the New Zealand study, said, “Early exposure in many areas is looking as if it’s more protective than hazardous, and I think we’ve just added one more interesting piece to that information.”

Dr. Hancox pointed out that the study does not show any mechanism to account for the association. “Even if we assume that the protective effect is due to exposure to microbial organisms, we don’t know which organisms are beneficial or how they actually influence immune function in this way.”

Thumb sucking, especially in an older child, can still be a problem if it interferes with the teeth, or causes infections on the fingers, or gets a child teased. Lynn Davidson, a developmental pediatrician who is an attending physician at the Children’s Hospital at Montefiore in the Bronx, and the author of a review article on thumb sucking, said she tends to be “very low-key” about thumb sucking, since children often stop on their own as they grow.

With older children, Dr. Davidson suggests that parents, if they are worried, should try to analyze when and why the child resorts to thumb sucking or nail biting, and then try behavioral techniques, like offering a child a foam ball to hold and squeeze at those moments. “In an older child you can use their input, ask, what would you do with your hands instead of putting them in your mouth,” she said.

Dr. Sears said, “My excitement is not so much that sucking your thumb is good as that it shows the power of a longitudinal study.” (A longitudinal study is one that gathers data from the same subjects repeatedly over a period of time.) And in fact, as researchers tease out the complex ramifications of childhood exposures, it’s intriguing to look at long-term associations between childhood behavior and adult immune function, by watching what happens over decades.

So perhaps the results of this study help us look at these habits with slightly different eyes, as pieces of a complicated lifelong relationship between children and the environments they sample as they grow, which shape their health and their physiology in lasting ways.

Learning to Live With a Child’s Allergies

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Credit Andrew Scrivani for The New York Times

When your older daughter is a toddler and you are pregnant with your younger daughter, your husband says, “Every Friday, we should have family pizza night.” Four months later, you give birth to a daughter who is allergic to milk (meaning also to cheese), as well as to eggs, tree nuts, peanuts and maybe buckwheat and flaxseed. Very early on, certain foods leave rashes around her mouth or make her vomit, so you stop giving them to her. When she is 8 months old, her sister spills ice cream on her arm. Red bumps immediately rise in the places the ice cream touched.

Your daughter’s allergies are officially diagnosed just before she turns 1, and for her first birthday, you make her a “cake” out of puréed sweet potatoes topped with coconut yogurt (you are now well-versed in the debate about whether coconut is a tree nut and think it’s not). She feels about this cake the way most anyone would, which is that it’s gross.

You scour the Internet for recommendations on how to handle multiple food allergies. You find horror stories about children dying of anaphylaxis brought on by a single bite of the wrong thing.

You read every ingredient in everything you buy at the grocery store, even when you buy more than one package of the same thing, even when you buy the same product week after week. You come to know certain products so well that when they get a new ingredient, it’s like a friend getting a haircut.

You talk to a fellow “food allergy mom,” the friend of a friend, who explains that your family shouldn’t go out for ice cream because even if your daughter gets sorbet, the employee will use the same spoon to scoop it that he used for someone else’s cone of pistachio; and your daughter shouldn’t eat jelly at another family’s house because that family dips their peanut buttery knives in the jelly when making sandwiches. You have always been such a good worrier, but these are things you never thought to worry about.

You stop going to restaurants as a family; you stop bringing home carryout, except occasionally and furtively, when you and your husband take turns eating it standing up in a corner of the kitchen (his preference) or sitting on the upstairs bathroom floor with the door closed (your preference).

You never leave the house without Epi-Pens.

Your husband, who barely cooked before you had children, matter-of-factly learns to make vegan doughnuts and vegan waffles and vegan whipped cream.

Because it’s medically recommended that you keep exposing your older daughter to the foods your younger daughter is allergic to, you go once or twice a week with your older daughter to diners or bakeries or Vietnamese restaurants. These are delightful outings — your older daughter is excellent company and loves trying new things — at the conclusion of which you scrub your hands and hers, at the restaurant and again at home, with a vigor appropriate for performing surgery.

When your daughter starts preschool, you burst into tears at the meeting with her teachers where you discuss how to handle snack time.

On Halloween, your daughter goes trick-or-treating but you carry along a bag of candy for her to choose from. Your daughter takes her own cupcakes to birthday parties and her own snack on play dates.

You rarely travel as a family; when you do, you pack loaves of bread and jars of sun butter in your suitcase. You FedEx soy milk to Idaho.

You wonder if it’s all because you ate too many peanut M&Ms when you were pregnant. At the same time, you decide that if you had it to do over again, the minute your daughter emerged from the birth canal, you’d have chewed up a peanut and spit it from your mouth into hers, because you’ve heard that pediatricians now endorse early exposure to nuts.

Other things you’d have done to prevent her allergies, if only time-travel were possible and if only you’d known: gotten a dog; renounced your dishwasher; become Amish.

You lie awake at night fretting about what will happen when your daughter is old enough for sleepovers, or for kissing people, or for college.

Those parents who complain about not being able to send their kids to school with the PB&J they love? Those airplane passengers who groan audibly when the flight attendant announces they won’t be serving peanuts today? Those codgers who say allergies didn’t exist when they were young and it’s just a bunch of helicopter parenting? You detest them.

But you feel enormous gratitude towards the parents who write “sun butter” on the plastic bags they send sandwiches to school in, or who go over the exact menu for their kid’s birthday party and show no irritation when they say, “Bagged carrots,” and you ask, “Bagged carrots that you’ll buy bagged or bag yourself?”

You start going as a family to an ice cream parlor where your older daughter and your husband get ice cream and you and your younger daughter bring coconut bars from home. You frantically wipe down the table and chairs before you sit. You know this excursion would probably seem depressing from the outside; secretly, from the inside, you consider it slightly depressing. But mostly you consider it festive and triumphant. Now your daughter knows what an ice cream parlor looks like!

You understand that into every life a little rain must fall but just wish the rain had fallen on you rather than your child. Obviously, to some extent, it is falling on you. But you wish it had fallen on you completely.

As much trouble as her allergies are, you never wish your daughter was anyone other than her hilarious, stubborn, singing, dancing, mermaid-obsessed, food allergic self.

And even if you cannot master allergies, it turns out that you can make cookies that are both safe for your daughter and delicious.

Allergy-Friendly Cookies

For a family with a child with allergies to milk, eggs and nuts, this is a go-to recipe.


Curtis Sittenfeld is the author, most recently, of the novel “Eligible: A Modern Retelling of Pride and Prejudice.” This is adapted from an essay in “The Artists’ and Writers’ Cookbook: A Collection of Stories With Recipes,” edited by Natalie Eve Garrett, to be published this fall.

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More Support for Early Exposure to Peanuts to Prevent Allergies

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Research found that feeding peanuts to young children starting when they are 4 to 11 months old sharply reduced the risk of their developing peanut allergies

Research found that feeding peanuts to young children starting when they are 4 to 11 months old sharply reduced the risk of their developing peanut allergiesCredit DeAgostini/Getty Images

LOS ANGELES — Evidence is accumulating that food allergies in children might be prevented by feeding infants peanuts and other allergenic food in their first year of life, researchers reported here Friday.

That finding would challenge the recommendation of the World Health Organization that babies be fed exclusively breast milk for the first six months of life.

“At least as far as peanut is concerned, I would recommend parting from that,” Dr. Gideon Lack, professor of pediatric allergy at King’s College London, said in an interview.

Dr. Lack was the senior author of a study last year that found feeding peanuts to young children starting when they are 4 to 11 months old sharply reduced the risk of their developing peanut allergies. That upended the conventional wisdom that it is best to avoid introducing peanuts until children are older.

Those results are already starting to affect feeding practices, but they left several unanswered questions. Now, some of those questions were answered by two additional studies that are being published in The New England Journal of Medicine and presented here at the annual meeting of the American Academy of Allergy, Asthma & Immunology on Friday.

One question was whether children who consume peanuts from an early age will still remain free of allergies if they stop consuming them. The researchers followed the children from the original study for another year, from the time they turned 5 until they turned 6. For that year, they were not supposed to eat peanuts at all.

The results were reassuring. There was no big increase in allergies.

“It tells you the protective effect is stable,” Dr. Lack said.

Another question was whether the early feeding technique could be applied to other types of foods and to children at normal risk of allergies. (The original study involved children deemed to have a high risk of peanut allergy.)

The researchers conducted a second study at King’s College London involving 1,300 infants who were 3 months old and being fed only breast milk. Half were randomly assigned to continue on only breast milk until 6 months of age, which is the recommended practice in Britain. The other half were to be regularly fed peanut butter and five other allergenic foods: eggs, yogurt, sesame, white fish and wheat. The children were assessed for allergies when they turned three.

Overall, 5.6 percent of the babies who were fed the allergenic foods early developed an allergy to at least one of the six foods, a modest improvement from the 7.1 percent in the breast-milk-only group. However, the difference was not statistically significant, meaning it could have occurred by chance.

One problem was that fewer than half the parents in the early-introduction group actually fed their children the required six foods on a regular basis. But when researchers looked only at those children whose parents adhered to the feeding regimen, there was a statistically significant reduction in allergies. Only 2.4 percent of those children developed a food allergy, compared with 7.3 percent of those whose parents faithfully stuck to breast milk only for six months. There were also significant reductions in peanut allergies alone and egg allergies alone.

One conclusion could be that feeding allergenic foods to infants early really does work to prevent allergies, providing that parents consistently do it.

But researchers cautioned there could be another explanation. One reason parents stopped feeding the foods is they perceived their children were having a possible allergic reaction to them. In that case, looking only at the children actually fed the food would overstate the effectiveness of the technique.

Dr. Lack said he did not think that was an explanation because the children in the early-introduction group whose parents did not adhere to the protocol did not have an unusually high rate of allergies at age 3.

In a commentary in The New England Journal of Medicine, Dr. Gary W.K. Wong, a pediatrician at Chinese University of Hong Kong, cautioned about jumping to conclusions. He said that in any case, the fact that so many parents did not stick to the regimen suggested it was too demanding to be practical, and that less burdensome ways must be found to introduce allergenic foods early.

“In the meantime,” he said, “evidence is building that early consumption rather than delayed introduction of foods is likely to be more beneficial as a strategy for the primary prevention of food allergy.”

The results of last year’s study on peanut allergy are already having an influence. The American Academy of Pediatrics and some other medical societies from the United States, Europe and several other countries issued a consensus statement calling attention to the findings that feeding peanuts starting early in life may prevent allergies. More formal guidelines are expected shortly.

A market might even be developing for baby peanut food. Dr. David Erstein, a New York allergist, started a company that sells a product called Hello, Peanut! — packets of peanut flour in measured doses that can be mixed into baby food to introduce infants to peanuts.

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