Sweet itch in horses is a worldwide problem affecting horses and ponies, and so far no cure has been found. However, there are various preventive and management approaches for this insect-hypersensitivity disease. The most effective way to prevent sweet itch is to avoid contact with insects. Good hygiene is also important for horses with sweet itch, and regular brushing and washing help keep the skin clean.
Sweet itch can develop in any breed, but breeds that are particularly prone include the Icelandic horse, Finnhorse, Shetland pony, Russ pony, and Friesian. According to research, susceptibility appears to be hereditary, and it is inherited more often from the dam than from the sire.
Symptoms
Symptoms of sweet itch often begin as itchy raised welts. This leads to rubbing to relieve the itch, which in turn causes mane and coat hair loss. Most commonly, the itchy areas are the back, the base of the tail and mane, the underside of the belly, and the head area. Rubbing breaks off mane and tail hair and damages coat hair, which leads to increased skin sensitivity, skin damage, and inflammation. Some patients also develop severe flaking. Symptoms are most clearly seen in spring, summer, and autumn during the peak activity season of midges and other insects. In winter, a sweet-itch horse can often be identified by a thin, poor-quality coat. It is important to rule out other factors that can cause similar signs, such as external and internal parasites, fungal skin infections, feed allergies, and protein hypersensitivity.
Protection
The most effective strategy is avoiding insect contact, and measures should be taken already before the grazing season begins and before the first insects appear. Insect contact can be reduced with, for example, insect repellents, an itch rug (often the most important protective measure, used throughout the summer), limiting turnout, or building insect-protective shelters outdoors.
Sweet-itch horses may be hypersensitive to harsh chemicals used in insecticides, so essential oil–based mixtures diluted in water or plant oil can be a good alternative. A very effective natural insect repellent is vinegar diluted in water; however, it stings badly if it gets onto broken skin. Another good option is a mixture of pine tar oil and cooking oil.
Support from feeding
The basic diet of all horses includes forage, concentrates, minerals and vitamins, and water. Every horse has individual nutrient needs that depend, for example, on breed, age, size, health status, and workload. For sweet-itch horses, there are several products intended to improve skin condition and coat quality.
The goal of feeding is not only to manage the condition, but also to enhance the body’s own function, metabolism, and immune defense in a natural way. Using nutrition—such as herbs or other natural nutrients—as part of health support requires commitment over time. Changes take time. The body’s cells renew relatively slowly, and you may need to wait up to three months to see results. For this reason, products intended to improve a sweet-itch horse’s condition should be started well before insect season begins, so the ingredients have time to take effect within the body.
Horses suffering from sweet itch are particularly prone to various deficiencies, and they often need additional vitamin and mineral supplements to meet required nutrient intake levels.
Vitamins
A vitamin D supplement is one of the most important year-round vitamin additions for a sweet-itch horse because the itch rug prevents the skin from producing vitamin D. Vitamin D regulates the calcium and phosphorus balance in the body, and deficiency can cause, for example, back pain.
Another important supplement is vitamin A, which is recommended at least in spring. However, remember that vitamin A deficiency—but also overdosing—causes skin problems. The safest way to ensure vitamin A intake is to feed carrots that contain carotene. Pasture grass is also a good source of carotene.
Of minerals, the most important for a sweet-itch horse is zinc, which has a major effect on skin wellbeing. Zinc levels in basic feeds are often low, which is why zinc supplementation is frequently necessary. When feeding zinc supplements, however, you must be attentive: too much zinc reduces iron absorption.
Flax, hemp, and chia
There are many different opinions about protein requirements and the impact of protein on horses with sweet itch. Many sweet-itch horses cannot tolerate feeds that contain large amounts of protein, such as red clover, silage/haylage, or alfalfa. Some owners therefore keep their sweet-itch horses on a diet with lower-than-normal protein levels.
At the same time, there are also many owners who believe that feeding high-quality protein improves sweet itch. No scientific research has been conducted on the benefits or harms of protein specifically for horses with sweet itch.
Flax has been observed to benefit individuals suffering from sweet itch. According to a study conducted by the University of Guelph’s equine research center in Canada, feeding flaxseed reduces skin symptoms associated with sweet itch. The study found that even large amounts of flax did not have negative effects on the horses’ fatty acid balance, but it clearly helped in the prevention and management of skin symptoms in horses with sweet itch.
Natural antioxidants are an effective aid against free radicals. They also reduce allergic reactions and promote faster healing of unwell skin. Chia’s nutrient composition is similar to flax, but its fatty acid and antioxidant profile is even better and richer than flax. Studies have also found hemp and hemp oil to be beneficial for horses suffering from sweet itch.
Herbs
When changing feeding—for example by using herbs—it is possible that the symptoms being supported may temporarily worsen. This is a sign of the body “activating” as it begins to cleanse itself of toxins and waste products. The more congested the body is, the stronger the cleansing reaction may be. This can appear as diarrhea, strong-smelling urine, coughing, mucus secretion, flaking, hives, and sweating.
During a cleansing reaction, it is not advisable to stop feeding altogether; instead, reduce the dose and reduce how often it is given. An interrupted herbal course may leave the horse struggling with waste products and toxins in the body. Allergic reactions to herbs are rare; however, if one does occur, the dosage should be reduced or feeding should be stopped completely.
In feeding, it should be remembered that supplements or feeds are not intended to replace medications prescribed by a doctor or veterinarian. For that reason, feed materials—such as herbs—should always be chosen carefully. When using herbs, you should familiarize yourself with their side effects, dosage, and interactions with other medications. The safest approach is to have the herbs you plan to use checked with your own doctor.
Natural plants that can support itching relief and skin health include, for example: dock, chamomile, calendula, wild pansy, chickweed, purple loosestrife, beetroot, heather, sea buckthorn, brewer’s yeast, peppermint, Boswellia serrata, dandelion root, black cumin seed, milk thistle seed, and garlic.
Today, closeness to nature and natural approaches are a continuously growing area of interest, and these methods are gaining more and more supporters. Feeding is also considered an important component of equine wellbeing and the management of sweet itch. What often comes up today specifically are natural food ingredients and removing industrially produced feeds from the diet.
Source: Hevosten kesäihottuma ja sen hoitomuodot. Satu Marttila, Hämeen Ammattikorkeakoulu, maaseutuelinkeinojen koulutusohjelma. http://www.theseus.fi/bitstream/handle/10024/66176/Marttila_Satu.pdf.pdf?sequence=1
