Antihistamines
Doctor, Should I Take Benadryl?
Should I take Benadryl for my rash? This is a VERY common question in a dermatologist’s office. Followed by, should I use Benadryl cream? So, I thought it was time we discuss antihistamines.
Antihistamines are a large class of drugs that target a group of receptors called histamine receptors. There are four types of histamine receptors in the body: H1, H2, H3, and H4. In dermatology, we are usually looking at the H1 receptors. The H1 receptors and therefore blocking of the receptors are involved with itching and rash.
There are a few different generations of antihistamines.
First Generation- In dermatology, we primarily prescribe these for their sedating effects to reduce itching. Hydroxyzine is by prescription, and Diphenhydramine (Benadryl) is available over the counter. The negative of these drugs is their sedating effects. Hydroxyzine has recently been classified as a high-risk medication in the elderly. This high-risk classification comes from worries of a fall while drowsy and limits the prescribing and recommendation of hydroxyzine. These medications are also short-acting. I like to think of them as RESCUE medications. However, in the case of hives, AKA urticaria, we are trying to PREVENT instead of RESCUE. I pretty much never recommend topical Benadryl. It does not work well for most patients, and allergic reactions to it are common.
Second Generation- In many cases, we want to prevent itching and hives. Second-generation antihistamines work best in these cases. This class has much less sedation and risk. More importantly, therapeutically, this class has the added benefit of longer action and, thus, can PREVENT the inflammation caused by histamine. This class includes loratadine (Claritin), Cetirizine (Zyrtec), Levocetirizine (Xyzal), and fexofenadine (Allegra). These are now OTC, and many are available in generic, making them affordable options. Most of these are standardly dosed once daily. However, when treating hives or urticaria, we may need to increase the does up to four times the standard dose. These medications are taken EVERY DAY as a preventative measure, not as a RESCUE.
Other than sedation, the side effects of antihistamines can vary from person to person. Common side effects can include urinary retention, constipation, dry eyes, and blurred vision.
Final thoughts when selecting an antihistamine: consider sedation, how long you want it to las,t and whether you want to PREVENT or RESCUE. Hopefully, this article will help you make wise choices in the future.
If you have any additional questions about antihistamines, ask your primary care doctor or pharmacist before taking it.
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