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When horses are stabled for long periods, we not only change their immediate environment but the temperature and humidity changes, too.

We do not yet fully understand all the environmental triggers that contribute to skin disease but it is clear that marked seasonal trends do exist.

The onset of warm weather regularly presents a new set of problems. Allergies can appear as itchiness and irritation often around the mane and tail. Pollens and flies are the likely cause of this type of summer allergy.

Summer problems

Sweet itch, caused by a reaction to biting flies, is the archetypal summer allergy. However, both fly bites and pollens can result in urticaria, as well as sweet itch. This disease sees the horse’s body erupt in often ever-expanding, swollen wheals, particularly on the flanks and neck.

Eosinophilic granulomas are small, hard nodules typically found on the flanks of the horse. When these occur during the summer they are usually associated with the same summertime triggers.

Stabling in bad weather

Identical allergic reactions often occur in horses when they are first stabled due to bad weather. The triggers for these allergic reactions are poorly understood. Where a direct correlation is seen with the signs starting after stabling, then factors in the environment must be the most likely suspects.

In many situations, a clear trigger can be identified. Food changes can easily be accomplished to avoid any of the components of the diet introduced on stabling. Changes in bedding can also be undertaken to eliminate potential allergens such as straw or shavings.

Haynets can be soaked so that pollen grains swell and reduce their allergic properties. However, despite rigorous changes, there are still many cases where the allergic trigger remains unestablished.

Unless further investigation is undertaken, these horses may be condemned to itch and irritation or steroid therapy. Intradermal allergy testing is used by dermatological specialists to try to establish other more subtle triggers.

Fungal moulds have been implicated as a cause of urticaria in man. Isolation of suspect moulds in the stable and correlation with positive reactions on allergy testing may help in management.

In the same way that asthmatics become unstable in the autumn, it is possible that allergic horses may develop itches, wheals or lumps as a reaction to stable mites.

Many symptoms will disappear completely once they are outside away from the allergic factors that drive them mad. For others, it will only be a brief respite before the pollen levels rise and the biting flies are back again to renew old acquaintance.

These are all treatable conditions, which can, in most cases, be improved by medication and change of management, so consult your vet for advice.