Each Kenalog injection contains Triamcinolone acetonide 40mg/1ml as the active ingredient. Triamcinolone acetonide belongs to a group of medicines called corticosteroids (steroids). The principal effect of corticosteroids is to reduce the body’s inflammatory & allergic response and they are used very commonly for many serious medical conditions. 

The hay fever injection works by temporarily suppressing your body's immune response for long enough to relieve symptoms. The steroids are injected into the buttock – known as an IntraMuscular (IM) injection – depositing a low dose directly into the muscle. They slowly leak into the bloodstream over the course of three weeks.

Once the injection is administered, the effects last for a minimum of three weeks, with many people experiencing relief from symptoms that lasts the entire season. Usually one dose of the hay fever\ injection, equivalent to 40mg triamcinolone acetonide, is enough. It's not recommended that anyone have more than two injections per hay fever season.