There’s good news and bad news: Spring is in the air. And with it, pollen.

Many people who take antihistamines — allergy meds — use these medications incorrectly. Here are five must-know antihistamine facts from a McMaster and University of Toronto study published this week in the Canadian Medical Association Journal.

1. First-generation antihistamines are associated with substantial and sometimes fatal side effects. Antihistamines with diphenhydramine, chlorpheniramine or hydroxyzine can cause drowsiness and affect cognitive function, including school performance. Overdosing on first-generation antihistamines can be fatal.

2. Newer antihistamines are safer, as affordable and as effective as first-generation antihistamines. Later-generation antihistamines are proven to be more effective and last longer with less side effects like drowsiness.

3. Most antihistamines are safe to use during pregnancy and breastfeeding.
Medical research has shown that antihistamines at standard doses do not harm fetuses and may be used during breastfeeding. They are also safe for children to use.

4. Antihistamines should not be used instead of epinephrine to treat anaphylaxis. Oral drugs can be used along with epinephrine injections to treat anaphylactic reactions, but they are not a substitute.

5. Antihistamines are very commonly — and often incorrectly — used. Antihistamines can relieve symptoms of hay fever and outbreaks of hives, but shouldn’t be used to treat asthma, eczema, coughs or insomnia.

Derek Chu, study co-author and McMaster allergy expert, says that it’s important for people to rethink what they stock in their home cabinets based on these five facts.

“People also need to rethink what hospitals keep on formulary, and what policymakers recommend. The message needs to get out,” says Chu. “This publication is on time for the spring allergy season and as COVID vaccines roll out, for which rashes are common and antihistamines can be helpful.”

No external funding was received for this CMAJ article.