Dr. Miller: You've had a big reaction to a bug bite. When should you see a physician? We're going to talk about that next on Scope Radio. I'm Dr. Tom Miller.
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Dr. Miller: I'm here with Dr. Mark Eliason. He is an assistant professor in dermatology. Mark, sometimes I have patients come into the office with a large, red, inflamed area where they've been bitten either by a tick or even stung by a wasp, or a bee, and my understanding is that they don't necessarily need to be treated for an infection, but this is just a reaction to the sting that may take a few days to go down. Could you comment on that?
Dr. Eliason: Sure, I'd love to. So when we get a bite or a sting or some sort of an insect penetrates our skin in some way, it can often look very impressive. People can get reactions that range from the size of a dime to the size of your hand, and even though it's large and it can be very frightening to see that, it often is something that is self-resolving, and it will get better whether it's treated or not.
Dr. Miller: Now sometimes these patients will seek antibiotics thinking that it is an infection and they need to be treated, but my understanding and training has been, no, in most cases, that's not true.
Dr. Eliason: That's right, and it's a hard thing to sometimes make a distinction for because when someone has a real infection, the skin is red, it's hot, and it often hurts. These bites can also be red and they can be swollen and sometimes it will overlap with the systems that we are worried about, but there are some things you can watch for that can help you understand, is this something that's worrisome enough it should be treated with prescription medication, or can some simple maneuvers at home take care of this.
Dr. Miller: Now what kinds of medications other than antibiotics might affect or help with this kind of a large reaction?
Dr. Eliason: In most cases, these reactions, especially the ones that happen quickly within a couple of hours from the bite or the sting, are mediated or caused by a molecule in your skin that's called histamine. Therefore, medicines that are antihistamines such as Benadryl and Allegra and Zyrtec are my first-line treatments for these. These usually work pretty fast. You have to be aware, some of these are sedating, and so people that take them can get pretty tired, so when you pick them up, if you're not certain which ones make people tired and which ones don't, check with the pharmacist or ask if this is going to make you fall asleep when you're driving your car because you don't want to do that.
Dr. Miller: Mark, depending on which antihistamine you take, whether that's sedating or non-sedating, how quickly should you see a response in reducing the size of the bite?
Dr. Eliason: Sure, so the Benadryl seems to work a little bit faster, and for most people, within a couple of hours, the swelling starts to go down. That's not the case in all situations. Sometimes it takes a whole day to see the improvement. But generally, it's pretty fast. The non-sedating antihistamines like Zyrtec and Allegra are designed to stay in our system a little bit longer, that means it takes a little bit more time for them to have an effect, and so most people may take a whole day after they take those before they can see swelling improve.
Dr. Miller: Regarding one of the most common sedating antihistamines, Benadryl or diphenhydramine, which it's known as generically, would you recommend taking one or two pills at the beginning?
Dr. Eliason: Sure. It's often based upon weight. So an average-sized adult could actually take safely more than one Benadryl. I have some patients and of course we look at other medicines that they're on first to make sure this is okay, but they'll take between two to four Benadryl depending on what we're treating and if they're a large enough individual to take that, so a 70-kilogram/150-pound person can usually take 2 Benadryl very safely, and it does work better than just one.
Dr. Miller: So you might think that there would be an infection though it wouldn't be very common if the redness started to spread up the arm or if you developed a fever or if you had some of the other signs of infection, then at that point you should probably be seen by a physician.
Dr. Eliason: Absolutely. When bites or these reactions occur on the skin and they're symmetric, they look like a nice oval or a nice circle and they're kind of the same distance in each direction, usually that's associated with a local reaction to whatever the insect put in the skin when the bite happened. When they're spreading, when people get lines in the arms or someone's reporting that they're getting a figure, that's a horse of a different color, so to speak. Those are things that need to be addressed by a physician.
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updated: July 2, 2019
originally published: March 3, 2015
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