What is the difference between drowsy and non-drowsy antihistamines?

The main difference between drowsy and non-drowsy antihistamines lies in their chemical structure and how they affect your brain. Drowsy antihistamines are first-generation medications that can cross the blood-brain barrier and cause sedation, making them useful for nighttime symptoms or sleep problems. Non-drowsy antihistamines are newer, second-generation medications that don't cross the blood-brain barrier as easily, so they're designed for daytime use when you need to stay alert.

Key points:

Drowsy antihistamines have a calming effect on the body and are best used at night or when you don't need to remain alert
Non-drowsy antihistamines are preferred for daytime use because they're less likely to make you sleepy
The difference is due to how easily each type crosses the blood-brain barrier and affects your central nervous system
Even non-drowsy antihistamines can occasionally cause drowsiness in some people, particularly at higher doses

This text has been fact-checked for accuracy by medino's clinical team.