Hives

These blisters appear very suddenly and can cover a large area of the body following an insect bite. In general, they go away on their own, and homeopathic treatment with Apis mellifica helps to get rid of the swelling. If 12 hours later, the problem hasn't gone away, the vet should be called in.

Make sure that the respiratory tract, mouth and trachea are not affected, and that your horse is breathing normally. If in doubt, call in the vet for a corticosteroid injection.

As a rule, this type of urticaria does not cause itching.

Other insect bites

Insect bites often form large, hard pimples on the neck and flanks.

In most cases, they don't itch and disappear quickly.

There's nothing you need to do.

Tick bites

Tick bites are very characteristic.

They form a small oedema with a more or less infected hole in the center.

The "pimple" is hard and often has small crusts on the flaking skin. 

Treatment is not systematically necessary. A simple disinfection may suffice.