Sweet itch is the commonest summer allergy seen in the UK. Culicoides hypersensitivity is its official name because it is in fact an allergic reaction to the saliva of the biting Culicoides midge. There are several types of midge but commonly irritation of the skin is seen at mane, tail, on the head and sometimes underneath the tummy. Most horses that suffer from sweet itch are very itchy, and will traumatize their skin by biting and rubbing on anything they can find; this results in broken hairs, bald patches, sore and painful bleeding skin which can be quite distressing for all.
Sweet itch can be a distressing condition for horse and owner
Midges feed all night, but predominantly at dawn and dusk. They do not like windy environments as they are unable to fly against wind speed greater than 7mph. They are attracted by ponds, hedges and damp / warm areas. Some horses with Culicoides hypersensitivities will also be allergic to other substances which can make management even more difficult. As with all allergies avoidance of the cause is the best solution, but this is often easier said than done. Changing environment can have a dramatic affect e.g. moving from a heavily hedged low lying field with a pond to a field on top of a hill can help sweet itch sufferers. Midges do go into stables so people have used ceiling fans in stables to keep them out. Any netting used needs to be extremely fine to prevent this, also any fly rugs need to be fine enough to prevent the midges biting through.
Culicoides (biting midge)
Boett is probably the best known rug to help prevent sweet itch. The use of electric fencing to prevent ponies from rubbing does have some welfare implications as although you are stopping the pony traumatising itself dramatically you are not actually doing anything about the terrible itchiness it is feeling. Keeping the pony stabled from dusk till dawn is one of the most effective measures but is not absolute. The use of heavy grease products which prevent the midges from biting can be quite effective but not every one wants a pony covered in heavy grease.
Summer fly cream is bright yellow and makes it harder for the midge to bite if used on areas not covered by the Boett rug. The use of permethrin products such as Switch will also help but rarely entirely cure the problem, they act by killing the midges when they bite but there does not seem to be any fly repellent on the market that is effective and lasts long enough to be useful. Vaccination against Culicoides hypersensitivity has not yet been effective although desensitisation for other allergies has proved to be useful in certain cases.
As with all diseases prevention is better than cure and planning ahead for the summer season is vital for known summer allergy suffers. We sometimes use anti-histamines and since 2016 we have used a white liquid product which reduces irritation. Sometimes we have to use steroid therapy to break the itch cycle. De-sensitisation can also be considered.