How treatments work, contra-indications, and side-effects.

Oral Antihistamines and antihistamine eye drops

Oral antihistamines work by physically blocking the H1 receptors, stopping histamine from reaching its target. This decreases the 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.

Typical side effects of treatment

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.

Contra-indications with oral antihistamines include:

• 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.

Steroid Nasal Sprays

When sprayed into the nose, steroids reduce inflammation caused by histamine release in response to an allergen. This can help relieve symptoms such as sneezing and a runny or blocked nose. 

Typical side effects of this treatment?

• Stinging or burning sensation in the nose.
• Dryness and crustiness in the nose.
• Dry, irritated throat.
• An unpleasant taste in the mouth.
• Itchiness, redness, and swelling in the nose.

Contra-indications

Because the medicine is mainly absorbed in the nose, it has very little effect anywhere else in your body. Therefore, they are considered to be very safe to use. However, caution should be used if the following apply:

• Have recently had surgery on your nose.
• Have infection in your nose.
• Are pregnant, trying for a baby or breastfeeding.

Corticosteroid creams and ointments

Corticosteroid creams and ointments e.g., Hydrocortisone work by decreasing inflammation in the skin. They do this by modifying the functions of epidermal and dermal cells and of leukocytes participating in proliferative and inflammatory skin diseases. After passage through the cell membrane corticosteroids react with receptor proteins in the cytoplasm to form a steroid-receptor complex and in turn reduce swelling and inflammation. More information on their mechanism of action can be found here. Corticosteroid mechanism of action.  Side effects of topical corticosteroids are rare but include atrophy, striae, rosacea, perioral dermatitis, acne, purpura, hypertrichosis, pigment alteration, delayed wound healing and exacerbation of skin infection.

Remember to refer to individual product specific literature for any interactions or contraindications on all products.