Antihistamines
Antihistamines
How does the treatment work
Oral antihistamines work by physically blocking the H1 receptors, stopping histamine from reaching its target. This decreases your body's reaction to allergens and therefore helps to reduce the troublesome symptoms associated with allergy.Similarly to oral antihistamines, eye drops work by blocking H1 receptors to reduce the effects of histamine release. However, they work locally and therefore more rapidly to relieve symptoms like eye itching, tearing, redness of the white of the eyeball, and swelling in the tissues around the eye. But the relief they provide may last only a few hours; so multiple doses throughout the day may be required.
Oral histamines may cause headache, dry mouth, feeling sick, drowsiness & dizziness (less so with the newer antihistamines). Side effects of eye drops are generally local and are limited to irritation and stinging/burning.
- Acute porphyria
- Liver or kidney problems
- Benign prostatic hyperplasia in men
- Acute glaucoma or patients at risk of glaucoma
- Should generally be avoided in pregnancy and breastfeeding
Remember to refer to individual product specific literature for any interactions or contraindications.