Common antihistamine side effects include:
- difficulty concentrating
- dry mouth, nose, and eyes
- slow reaction time
You should discuss these side effects with your doctor if they interfere with your normal activities, or if you think they put you or someone else in danger.
Less frequent side effects include:
- appetite loss or gain
- poor coordination
You should discuss these side effects with your doctor if they interfere with your normal activities or if you think they put you or someone else in danger.
Rare side effects include:
- blurred vision or glaucoma complications
- difficulty sleeping
- difficulty with urination
- heart rate changes
- low blood pressure on standing
- muscle weakness
- vomiting, nausea
- nightmares (in children)
- restlessness (in children)
- irritability (in children)
Talk with your doctor if you experience any of these. If you're bothered by side effects, your doctor can often help by changing:
- How much medication you take. Sometimes side effects can be stopped or minimized by reducing the dose. Or, your doctor may lower the dose and then raise it more slowly.
- When you take the medication. You may be able to cope with drowsiness or insomnia, for instance, by taking your medication in the evening or first thing in the morning.
- How you take the medication. Taking your medication in smaller doses several times a day rather than in one dose can help. Taking it with food might eliminate side effects such as nausea.
- The type of medication. A different medication may stop your symptoms with fewer or less severe side effects.
Always talk with your doctor before changing how you take medications. See the next page for more information about allergy medications.