Why do I feel sleepy after taking allergy medicine?

Many allergy medicines, especially older types known as first-generation antihistamines, can make you feel sleepy. These medicines work by blocking histamine, a chemical in your body that causes allergy symptoms. However, histamine also helps keep you awake. When antihistamines block histamine, they can make you feel drowsy.

Why Do Antihistamines Cause Sleepiness?

1. Central Nervous System Effects: Some antihistamines can cross into the brain and affect the central nervous system, leading to sedation or sleepiness.
2. Types of Antihistamines: First-generation antihistamines are more likely to cause drowsiness than newer ones. Newer antihistamines are designed to not enter the brain as much, so they usually cause less drowsiness.

Tips to Avoid Sleepiness

• Choose Non-Drowsy Formulas: Look for allergy medicines labeled as 'non-drowsy.'
• Timing: If you have to take a drowsy antihistamine, consider taking it at bedtime.

It's important to read the label and talk to a healthcare provider if you have questions about which allergy medicine is right for you.