Sweet itch

Sweet itch is the most common equine allergic skin disease in the UK and it affects around five per cent of our horse population. In its simplest form, it’s an allergic reaction to bites from biting insects. It can affect almost any horse or pony – regardless of type, breed and age – but research does show that sweet itch is particularly prevalent in some native breeds. 

The insects that cause the hypersensitivity differ depending on the country, but in the UK these are the black fly (Simulium) and the midge (Culicoides). While we tend to think of sweet itch as a summer condition, these biting insects are active from March to November.

Did you know? 

Horses who are affected by sweet itch develop increasingly severe symptoms over time.

Spot the signs of sweet itch

The condition causes itching, known as pruritis, which varies from the horse who occasionally rubs his tail on a tree to the very worst cases who will scratch and scratch, causing self-trauma. Likewise, some are severely affected after one or two bites, whereas others only suffer mildly after several. Whatever the severity, it’s important to spot signs early, because the earlier sweet itch is diagnosed and treated, the better the chance of being able to manage it effectively.

Signs to look out for include…

• itching that’s focused on the neck, mane and tail, although the worst affected horses may end up rubbing and biting at their skin wherever they can reach 
• ruffled, rubbed hair or hair loss in affected areas
• lumpy or scaly skin in rubbed areas, which is usually inflamed or hot to the touch. The skin may also be thickened and bleeding  
• scurfy, dull skin in patches 
• restlessness due to discomfort
• weight loss in the very worst cases

How to diagnose sweet itch

If your horse is beginning to show possible signs of sweet itch, the first thing is to confirm it’s definitely the problem. There are many other allergens that cause the same or very similar clinical signs – for example, a horse with a severe allergic skin condition resembling sweet itch could simply be suffering from an allergy to something as innocuous as carrots. 

Initially, it’s worth implementing measures to limit your horse’s exposure to flies and midges. If the condition doesn’t improve, then you’ll need to speak to your vet about intradermal allergy testing. This involves injecting midge extracts and other allergens into the skin to see if they cause a reaction. There are also various blood tests that claim to be able to detect allergies, but there’s limited evidence to support their use or reliability.  

How to prevent sweet itch

When it comes to sweet itch, prevention really is much better than cure, so it’s important to start protecting your horse before the midge season hits – once he’s been bitten and a reaction starts, controlling the condition will be more difficult. There are several ways you can minimise his contact with these insects…

• fly rugs are becoming increasingly sophisticated, with a wide variety on the market to suit a range of budgets. Horses who are severely affected usually need to wear a fly rug all the time, so it’s worth investing in one that fits well, and is comfortable and hard-wearing. You can even purchase rugs that are specially designed to fit different shapes or types of horse. Some rugs simply cover the body, neck, tail and under belly area, while others quite literally encase almost every inch of his skin to ensure as little is exposed to biting insects as possible  
• fly repellents and insecticides can come in the form of sprays, creams, bands and tags. Look for products with pyrethroid or permethrin-based ingredients, because these are often the most effective. DEET is also effective, but do a patch test first to ensure your horse isn’t sensitive to it
• stabling your horse at dawn, early evening and dusk is advised, because this is when biting insects tend to be at their most prevalent, although this will vary depending on your geographical location, the time of year and what’s practical for you as an individual
• cover stable windows and doors with ultra-fine midge screens to keep the insects out 
• spray his stable with insecticide
• install fans in his stable – midges can’t fly in a strong breeze
• avoid areas of standing water, as this is where midges lay their eggs
• avoid thick tree lines, which is an environment favoured by midges
• turn him out in an open, windswept area – a paddock on top of a blustery hill is best

Did you know?

 While the insects that cause sweet itch are active between March and November, horses with severe symptoms can experience problems all year round. 

How to reduce itching

Unfortunately, there’s no cure for sweet itch, it’s simply a case of putting measures in place to stop the midges biting wherever possible. 

Steroids can offer relief from the skin irritation and itching in the short to medium term, however, over the long term, they increase the risk of laminitis, so it’s not a sustainable solution. In some cases, antihistamines can help relieve the symptoms, but they need to be administered in relatively high quantities, making this an expensive and often ineffective option. A good option for short-term relief is bathing the affected areas with ice or cold water. 

Research has shown that omega-3 and omega-6 fatty acids can be effective in reducing itching, so it may be worth feeding linseed or evening primrose oil in case this offers your horse some relief.  

Different solutions work in varying degrees for different horses, so there’ll be some trial and error in order to find what’s effective for your horse. 

Prevention is key

While not life-threatening, sweet itch causes immense distress to severely affected horses and is a major welfare concern when not managed effectively. A combination of preventative measures and seeking appropriate treatment as soon as signs develop will help to manage the problem and make life as comfortable as possible for your horse.