Sweet itch is a skin disease caused by an allergic reaction to the saliva of culicoides species (midges), characterised by intense itching. After an allergic horse is exposed to the saliva the immune system will produce an excess of histamines similar to that of people suffering from hay fever. This is an ‘over the top’ immune response resulting in swelling and intense itching of the skin causing the horse to rub and chew at the area affected. The most severely affected areas tend to be along the mane and tail base resulting in the horse rubbing out large sections of hair to leave thickened, rough, hairless and often raw skin. The skin can then become infected thus making the condition worse. Signs can start at a very young age and tend to become more severe year on year although some horses can develop the allergy later in life. It can be a very debilitating condition throughout the warmer months when the midges are most active and affected horses can become very miserable.
As this is an allergic condition it only takes a few midge bites to trigger the symptoms and the key to control is reducing/preventing attack. A number of management changes should be implemented:
- Environment – Midges breed on wetland/near water sources and woodland. Susceptible horses should avoid these areas. A windy hillside is best for keeping midges away!
- Stabling – Midge activity is highest at dawn and dusk so stabling susceptible horses from 4pm until 8am during the summer is best. You can fit fly screens to the stable door and use insect repellent strips to ‘midge-proof’ your stable. A fan in the stable creates air movement so keeping midges away as they cannot fly against a wind stronger than 5mph.
- Rugging – placing a full body lightweight sheet on your horse including hood, tail cover and belly protector will prevent midges from biting.
- Fly repellents – should be applied liberally particularly along the crest, spine, tail and head especially when riding your horse. There are many products available (some more effective than others!) SWITCH and DEOSECT can be very effective and don’t need applying everyday.
Despite your best efforts at prevention many horses still get ‘sweet itch’ and it is important to discuss treatment options with your vet.
- Topical creams – those containing steroids and anti-histamines can be of use, they can expensive longterm but judicious use can help to alleviate symptoms.
- Anti-histamine tablets – sometimes of use but often ineffective due to severity of allergy
- Steroid treatment – injection with steroids helps to reduce the immune response to the insect bites and long acting preparations can give several weeks of relief. Steroid treatment does not treat the underlying condition but merely relieves the itch. It should be used with caution at the lowest possible dose due to potentially serious side effects including laminitis, however sometimes it is the only option to relieve the horses discomfort.
- Cavalesse – this is a natural food supplement containing vitamins and minerals which have a specific effect on the immune system within the skin. A key ingredient, nicotinamide, acts to reduce the production of histamine (which causes the itch) and to improve the skin oil barrier by increasing the amount of natural fats at the skin surface, thus acting as a natural barrier to midge bites. This product works best if treatment is started at least a month before the allergy season and continued throughout the risk period.