A rash may not be an allergy

Gordon wrote in: “My son had some pink spots after taking amoxicillin years ago. They still say he’s allergic and can’t take it again. How do they know?”

As with all of the material on this site, the information here is for general educational purposes only. I am not your doctor, or your child’s doctor; even if I am, this isn’t specific medical advice. Drug allergies do occur and they can be serious, and though re-exposing a child thought to be allergic to a drug may be safe, it should only be done with his own physician’s specific instructions and guidance. Don’t follow any sort of advice from any web site, especially mine; in fact, you should probably stop reading this now and go clean your eyeballs with Lysol. Wait, don’t do that either. Just sit there quietly. Please, don’t sue the nice doctor.

Though many people recall that they or their kids developed a rashes after taking an antibiotic, most of the rashes are not allergic, and won’t recur. Studies of adults who have had a rash after penicillin and think they’re allergic have shown that fewer than one in ten will have any problems if they take the same antibiotic again.

Drug rashes that are truly allergic in nature usually appear as hives, or “urticaria.” These are raised, itchy areas that quickly appear and disappear. Other serious rashes can be accompanied by red lips, red eyes, vomiting, flushing, dizziness, trouble breathing, or fainting. If your child has had a rash that includes hives or other significant symptoms, it’s not a good idea to try the medication again without very strict supervision. Not only are rashes like these likely to recur, but they may get worse upon re-exposure.

More mild rashes are most typically flat or nearly-flat pink spots that blanch, or disappear, when the skin is stretched. Mild rashes will not be accompanied by other significant symptoms. These sorts of rashes are not allergic, and will usually not recur if the medicine is taken again; if they do recur, they don’t tend to get worse or more serious.

If your child has had a rash or other reaction to a medication, take photos and keep track of exactly what happened. If a baby has even a mild rash with an antibiotic, pediatricians may be especially reluctant to try the medicine again until the child is older—at least old enough to talk and explain any symptoms that might occur. But by then, memories fade, and often the medication is kept on the “allergic” list unnecessarily. Keeping track of the exact reaction can help your pediatrician decide whether re-challenge is a good idea.

What about allergy testing, to be sure? There is currently no good standardized, reliable test for amoxicillin (or any other drug) allergy. The “test” is the history of what happened with the exposure; the only way to be sure is to take the medicine again and see what happens. An allergist can sometimes use a “home brewed” kind of skin test, but that’s rarely necessary and not always accurate.

A family history of allergy does not mean that a child is allergic. If mom or dad had a reaction to penicillin, even a serious one, penicillins are not more likely to react in the child than any other medication. If a parent’s reaction was severe, for peace-of-mind it may be reasonable to avoid the medicine in a baby, but it doesn’t mean that the medicine should never be used.

Sometimes, when a child is thought to be allergic to one antibiotic, it’s assumed that other antibiotics in that same family will also trigger problems. In the past, it was thought that anyone with a penicillin (or amoxicillin, or ampicillin) allergy couldn’t take any antibiotics from the class of “cephalosprorins,” like Omnicef, Ceftin, Vantin, Keflex, or many others. Good studies have shown that this is not true. In most circumstances these medicines are not cross-reactive. I get a lot of phone calls from well-meaning but ill-informed pharmacists on this point: just because Junior had a rash with amoxicillin, it does not mean that he shouldn’t take Omnicef. (I keep a copy of a good authoritative article on this from 2007 to fax to pharmacies.) Again, your own physician who knows the details of the reaction should help decide this, but doctors and pharmacists should not always assume that penicillins and cephalosporins (or other medicines that are in the same families) are cross-reactive.

Antibiotics and other medicines should not be used unnecessarily. If your child has an infection that’s viral or will improve without treatment, there is no reason to take antibiotics. But if your child does need to take a medicine, having a history of a mild rash in the past doesn’t necessarily mean that the medicine should never be used again. Discuss the pros and cons of re-exposure with your physician. If you or your child are taking a medicine and develop a rash or any other side effect, speak with the physician about whether to discontinue the medicine, and whether it might be safe to try that medicine again at a later date.

Nuts. Allergy!

Allison, whose name was ranked #47 among newborn girls in 2007, has a question about nut allergy: “We just (inadvertently) figured out that our 6 year old son is allergic to pecans. His reaction isn’t life threatening — his eyes swell up and get itchy. What should we do (other than obviously teach him to not eat pecans)? Do we need to get him tested officially? Tell the school? Anything else?”

The first step, as you said, is to avoid pecans: teach him not to eat them, and to ask adults about the nut contents of food, and get used to reading labels on things like cookies or brownies. Since he might not be able to tell the difference between a pecan and another nut by just looking, it’s probably best for him to learn not to eat anything that looks like a nut unless it’s OK’ed by you. Definitely, tell the school, tell grandma, and tell any of his friend’s parents before you drop him off for the afternoon.

You should also travel with Benadryl at all times, and keep some in your house. Make sure grandma has some too. Talk with your pediatrician about specific dosing and usage of medications, and whether you ought to carry injectable epinephrine. People at the highest risk for life-threatening nut allergies are those who have had any sort of nut reaction in the past and who have a history of asthma or wheezing.

Allergy testing can be useful to see if he’s also allergic to other tree nuts, or to peanuts (there are often cross-reactions.) If he’s already had peanuts and other kinds of nuts, and never reacted, there is no need for testing. But if you’re not sure if he’s had different kinds of nuts, it’s a good idea to do a “nut panel” to see if he’s likely to be allergic to other nuts.

Visit the Food Allergy & Anaphylaxis Network for more info—it’s an excellent, non-profit web resource with good info on nut and other food allergies.

Peanuts, when?

Gretchen asked, “When is it ok to feed a child peanut butter? I have heard that you should wait until 4 years old because if you try sooner then the child could become allergic. I have been feeding my 14 month old peanut butter since his first birthday and he has shown no signs of allergy, but can he develop one if I give him peanut butter too often (another rumor I have heard)? He eats it about 3 – 4 times a week.”

There is no consensus among allergists or pediatricians about when kids can safely start peanut butter. There is no “official” recommendation from either the American Academy of Pediatrics (AAP) nor the American Academy of Allergy Asthma and Immunology (AAAAI). Since there’s really no evidence that delaying introducing peanuts prevents allergies, there’s no good reason to delay peanuts as long as many people suggest.

For a long time, a strategy proposed to prevent allergy was to delay introducing certain foods. You’ll find all sort of tables with specific “recommendations”—strawberries at 12 months, or peanuts at 3 years, or whatever. But until recently there really was very little research to help guide these sorts of suggestions. The tables were arrived at by a process of “expert consensus,” a fancy term for “making things up.”

The best recent studies, summarized here, do not support delaying food introduction. In fact, some studies have found that by delaying certain foods, you might increase your child’s risk of allergy.

Keep in mind that your child’s risk of food allergy depends very much on the parent’s history. If neither parent has food allergies, a child has a very low chance of food allergy, less than 2%. If one parent has a food allergy, it’s up to 8%; if both parents have food allergies, their child has about a 50% chance. You could also consider siblings—the more siblings with allergy, the higher the chance. And once a child has one food allergy, the risk of having others is fairly high. So if there is no family history of allergy, and a child hasn’t shown signs of any other food allergies, the chance of a peanut allergy is very small.

Since your child is tolerating peanuts fine, there is no reason to restrict them. It is not true that frequent peanut ingestion can lead to allergy. Your child can continue to eat peanut products safely as often as he’d like.

I routinely suggest that children who don’t have a strong family history of allergy can start having peanut products at twelve months of age. It’s important for all families to keep Benadryl in the house, and know their child’s dose (ask your pediatrician.) If a rash develops after peanut (or any other food) is ingested, give Benadryl. If there are any signs of trouble breathing, tongue swelling, or decreased consciousness, call 911. If you’re not sure what to do, contact your child’s pediatrician immediately.

Mystery hives

DMT asked, “My daughter is almost 2 and has had several bouts of hives. The first bout or two lasted only a day or two. The third lasted for 8 days, and the fourth for 10 days. They come and go in patches in the matter of an hour or two, and I have been told numerous times that it is a virus. We have been to an allergist, and he does not believe it is due to allergies, either. She has been on Zyrtec for about 1 month. One day, I forgot to give it to her in the am, and she had 2 little hives. Today, she spit the Zyrtec out (and I did not attempt to give her more), and she woke up from her nap with 4 or 5 huge hives. This is leading me to believe it is allergy based. Any ideas?”

This comes up frequently, and I’m glad you asked about it. Many doctors are getting this wrong, and it’s causing more grief for families than the hives themselves.

First: If your child has hives accompanied by difficulty breathing, unconsciousness, or swelling of the lips, throat, or tongue, call emergency services (911) right away. Though most hives are not serious and do not lead to a more severe reaction, you need to react quickly to any reaction that includes difficulty breathing or a loss of consciousness.