Why do antihistamine sleep aids often cause morning grogginess?

Antihistamine sleep aids can make you feel sleepy the next morning because they have effects that last beyond the time you take them. This is known as a 'residual sedative effect.' According to research, these medications can affect how alert you feel, even after you wake up.

How Antihistamines Work

1. Sedative Effects: Antihistamines are designed to help with allergies, but they also make you sleepy. This is because they block a chemical in your brain called histamine, which helps keep you awake.
2. Lingering Effects: Some antihistamines stay in your system for a long time. This means they can keep making you feel sleepy even after you wake up.

What Studies Show

• One study found that the sedative effects can last into the next day, making people feel groggy in the morning.
• Another study showed that people might get used to these sleepy effects over time, but not everyone does.

If you are feeling very sleepy in the morning after taking an antihistamine, it might be helpful to talk to a healthcare provider about other options.