Horse Asthma, Allergies: Triggers and Solutions

People who spend a lot of time around horses know that like humans, horses can suffer from allergies and asthma. Now new research reveals that Fall can make both worse for horses, what the triggers are, how it actually affects horses, as well as remedies or workarounds.  Here are the takeaway findings from the research:

→ Horses can be affected by seasonal allergies. The symptoms can include: Nasal discharge, Frequent cough, Exercise intolerance, Increased respiratory rate and effort, Development of a ‘heave line’ (due to increased respiratory effort using chest and abdominal muscles), Acute attacks of respiratory distress due to repeated exposure to dust or pollens.

→ Equine asthma can flare up as a result of allergies, especially during the Fall.

→ The causes of equine asthma are largely environmental.

→ There is a tendency for an increase in horses showing signs of equine asthma during crop harvest season. (Horses pastured near fields where crops are harvested may be exposed to the dust generated by the combine harvesting crops.)

→ Most asthmatic horses are also allergic to hay dust–they usually develop clinical signs when fed hay in the barn during the winter months.

→ Horses affected by these hay dust allergies may develop signs like coughing or increased breathing efforts within a few days of exposure to the dust or allergens and may show impaired performance.

→ Some horses with asthma tend to exhibit symptoms when pollen and molds peak in the fall–while the triggers may be different, horses with these triggers will show similar symptoms to those horses whose asthma and allergies are triggered by hay dust allergens.

→ Mowing doesn’t seem to change what is triggering the disease for the summer-pasture form of equine asthma. It mainly seems to be eating from grass, rather than tree pollen, that is triggering these horses’ problems. It may be due to mold-type fungi that are on the grass that are the trigger, and not necessarily grass pollen itself.



→  Taking preventive measures can help minimize horses’ exposure to allergens and prevent asthma flare-ups, keeping horses healthy and performing at their best levels.

→ Horse feeding of round bales is associated with more severe signs because horses are exposed to higher dust levels compared with eating from square bales–This is especially true when round bales are left in the field uncovered as they tend to become moldy from exposure to rain and moisture.

→ Horses experiencing less severe asthma symptoms improve when they are on grass pasture. (Unfortunately this is not always possible during the fall months.)

→ Feeding horses low-dust forages can help horses recover and also prevent flare-ups of asthma and allergies.

→ Horses benefit from being fed steamed hay or haylage instead of dry hay. These forages result in lower exposure to dust as compared to dry hay, and this translates in lower levels of airway inflammation. Haylage appears to have the strongest beneficial effect, and this effect seems to be linked to higher omega-3 fatty acid content.

→ Avoiding exposure to allergy triggers, such as by feeding low-dust forages, can help horses stay healthy and perform at peak levels. During crop harvest season, this might mean keeping the horse in the barn while crops around the stable are harvested.

→ Additional supplementation with nutrients rich in omega-3 fatty acids, like EPA and DHA found in fish oil and algae, can help keep asthmatic horses healthy.

→If horses continue to show signs of asthma despite environmental management, your veterinarian may prescribe treatment with aerosolized corticosteroids.

Source: Dr. Laurent Couëtil, veterinarian and professor of large animal medicine at Purdue University, Director of the Equine Sports Medicine Center and of Equine Research Programs, Purdue College of Veterinary Medicine.