House CallJune/July 2009 Issue

Ask the Doctor

Pediatric allergists Harvey L. Leo, MD, and Neal Jain, MD, answer questions about allergies and food sensitivities.

Q. I see that the Food and Drug Administration includes coconut on its list of tree nuts. My little boy is allergic to tree nuts and peanuts. Must he avoid coconuts because of a potential cross-reaction?

A. The short answer is no. Coconut is not related to tree nuts nor is it related to peanuts. Coconut trees are part of the palm plant family Arecaceae, considered monocots. Trees that produce tree nuts are dicots, only distantly related to monocots. 

Although there are reports in the medical literature of some cross-reactivity between certain tree-nut proteins (like hazelnut and walnut) and coconuts, an allergy to coconut in nut-allergic patients is actually rare. A recent study found that patients diagnosed with a tree nut or peanut allergy had no increased risk for developing an allergy to coconut.

Bottom line: Allergy to coconut is rare, far less common than allergy to tree nuts or peanuts. There seems to be no association between coconut allergy and tree nut or peanut allergies.

As for your son, consult with a pediatric allergist to determine whether he is allergic to coconut.     
–Dr. Jain

Q. If I’m allergic to tree nuts, will I have a problem with nutmeg?

A. There’s no connection. Nutmeg is not a tree nut.
–Dr. Leo

Q. My child’s skin breaks out in welts and hives when he is lightly scratched and the rash lasts for hours. The doctor says he has dermatographism. Is this dangerous? 

A. Dermatographism is a condition where pressure on the skin causes the skin mast cells to release histamine, resulting in a raised rash or welts. A doctor sees this condition when parents bring their child in because they’ve noticed the rash. You can demonstrate dematographism, which literally means “skin writing,” by stroking the child’s skin with a blunt object (I often use a tongue depressor) and observing the welt develop within minutes on that spot.

Dermatographism is limited to the skin and is not life threatening. It has no relationship to food allergies or environmental allergies but it may hamper how skin tests are conducted. Although the condition may improve over time for some, many people remain dermatographic their entire lives. Some allergists prescribe an antihistamine to help reduce skin sensitivity but treatment isn’t usually necessary.
–Dr. Leo
Q. Can someone be allergic to mustard seed?

A. Yes. There are reported cases of people having anaphylactic reaction from eating food with heavy mustard content. Generally speaking, however, allergy to mustard seed (Brassica sp) is fairly rare in the United States. The condition is more prevalent in Europe, particularly in France where more mustard is consumed. Mustard greens, a food commonly enjoyed in this country, are unlikely to cause any significant reaction or allergy problems. If you suspect you have a mustard allergy, consult with an allergist.
–Dr. Leo

Q. Our 4-year-old daughter gets big welts from mosquito bites. Should we be worried?

A. Young children tend to develop large, very dramatic local reactions to mosquito bites, particularly when they’re bitten in sensitive areas like the face and around the eyes. Some kids develop periorbital cellulitis, a condition where the eye area becomes hot, red and infected. I’ve seen children whose eyes have swollen completely shut from a mosquito bite. As bad as they look, these reactions are considered within the normal range of illness and are not related to the type of allergic reaction caused by stinging insects like bees, wasps or fire ants.

There’s no standard allergy test for mosquito bites. Treatment is localized skin care, such as applying cool compresses or a topical, over-the-counter hydrocortisone cream. In severe cases, a doctor will administer a long-acting anti-histamine or resort to more aggressive treatment to keep the reactions controlled.

Given the fact that mosquitoes carry illness like West Nile virus, parents should be prudent about mosquito exposure and protect their young children. Use common sense. Clean out stands of water around your home, avoid being outdoors during dusk hours, use an appropriate bug repellent and keep your child’s delicate skin covered with long sleeves and pants.

Q. I’ve heard that taking probiotics when I’m pregnant and then giving my infant probiotics may help prevent her from developing eczema, food allergies and asthma. Is this true? Should I plan to give my newborn probiotics?

A. A number of studies have looked at whether ingesting probiotics late in pregnancy and in infancy reduces the likelihood of developing allergic diseases. Research suggests that probiotics may offer some protection but the effect seems to be temporary.

A study published in the Journal of Allergy and Clinical Immunology examined this question. Mothers at high risk for having allergic children were given probiotics during their last four weeks of gestation and their infants received probiotics during their first six months of life. The probiotics appeared to lower the rate of allergic eczema in many of these children up to age two but there was no difference in rates of allergic disease by the time the kids were five. Study participants received a specific combination of four different bacteria, plus a prebiotic. This means that results from this study (and others) may not apply across the board with other types of probiotics.

Current data is insufficient for making conclusive recommendations but eating foods that contain probiotics, such as yogurt or kefir, during the third trimester of pregnancy may offer health benefits. Additionally, there doesn’t seem to be any evidence to suggest that giving infants probiotics (such as lactobacillus) is harmful. As such, it may be worthwhile to supplement your infant’s diet with probiotics, particularly if there’s a strong family history of eczema and allergies. Consult with your pediatrician. 
–Dr. Jain

Harvey L. Leo, M.D., is a pediatric allergist with Allergy and Immunology Associates of Ann Arbor and an assistant research scientist with the Center for Managing Chronic Disease at the University of Michigan.

Neal Jain, M.D., is a pediatric allergist with Dean Health System in Madison, Wisconsin, and an assistant clinical professor of medicine at the University of Wisconsin School of Medicine and Public Health.


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