These symptoms are caused by an allergy to pollen, and just like humans horses can also suffer from pollen allergies, leading to coughing, head shaking, lethargy, poor performance and can lead to issues with concentration and behaviour.
Pollen allergies are very common in horses of all types and ages. Every spring and summer billions and billions of tiny pollen particles are released from grass, plants and trees. The function of the pollen particles is to fertilise other plants, but many are inhaled by animals and for those who are allergic to them, trigger reactions. Scientists are unsure why some horses (and people) are more sensitive to allergens, but it is clear what happens when the body is exposed to them!
The horse’s nose acts as an air filter, with hairs stopping foreign particles entering the lungs. If there is a high pollen count, these hairs will be trapping lots of pollen particles. If the horse doesn’t have a pollen allergy, this is a very good defence. However, when a horse has a pollen allergy, the pollen triggers a reaction as if a harmful substance is present, nerve signals cause blood vessels to dilate and inflammation occurs, which leads to the coughing and head shaking we associate with the problem.
Normally the horse will have a specific pollen that they are allergic to, and by identifying the problem pollen you can try to avoid it, for example, if your horse is sensitive to Oilseed rape pollen (this allergy usually is seen from the end of March to mid-July, peaking in June), try to avoid hacks near rape fields where possible, and chose competing venues that are not surrounded by the crop.
In addition to this, there are certain management steps that can help your horse, such as using a pollen net or face mask to help ease coughing, nose itching and head shaking while riding, and stabling during the day and turning out at night can sometimes benefit horses with pollen allergies. In extreme cases, do not ride on days when pollen counts are high and where possible try not to go into the vicinity of the offending pollen.
Olivia Colton MSc
Nutritional and Technical Coordinator