Detection and Treatment of Allergies

Skin tests, Antihistamines, Adrenaline and Allergy Advice

Skin Tests

Skin-pricking test

Simple, quick, inexpensive. Suitable for most patients, except those who have suffered an anapylactic shock. Can test 3 - 25 allergens

Usually done on the forearm. Those with eczema may have it done on their back. The arm is marked with code numbers for the allergens being tested.

A drop of the allergen or solution with an extract of it is placed by each code. A positive control (histamine) and negative control (saline) are also used.The skin is pricked through the dot with a sterile needle. 

If there's a positive reaction, that spot becomes itchy and swollen in minutes.

Patch testing

Tests for skin allergies. Allergens are applied to skin on back in petroleum jelly on hyperallergenic metal disks. The disks are held on with hypoallergenic tape. 

The skin is coded & after 48 hours the skin is checked for irritation.

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Antihistamines are drugs which prevent histamines from binding to histamine receptors, preventing the symptoms of allergy.

They are available as tablets, creams, eye drops, sprays and injections. 

Older histamine drugs affected histamine receptors in the brain, causing drowsiness. Recent drugs have less of an effect in the brain, and also last for longer so medicine isn't taken as frequently.

Some can be bought over the counter, others have to be prescribed.

Can be used in emergency treatment of anaphylactic shock as an injection after an adrenaline injection.

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Adrenaline binds to adrenergenic receptor molecules which are found on cell membranes, especially in the heart, lungs and blood vessels.

When an adrenaline injection is given the heart beats faster and more strongly.

Tthe smooth muscles in the walls of the bronchioles relax, widening the airways.

Smooth muscle in the walls of the arterioles contract, narrowing the lumen, increasing blood pressure.

Relieves itching, redness and swelling.

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