Dogs, like humans, can also get allergies. It is often difficult to determine the cause of an allergic reaction in dogs.
An allergy is defined as excessive activity of the immune system. The allergen, a substance which is harmless in itself, triggers a strong immune response in the form of inflammation. In humans this can lead to hay fever and watery eyes, and can also cause itchiness, reddening of the skin and digestive problems depending on what part of the body is affected.
For dogs, the case is similar: contact with the allergen - whether in the air, through skin contact or in food - leads to a strong immunological defence reaction. In our four-legged friends it is predominantly the skin that is affected. Itchiness causes them to scratch themselves until the skin is raw or lick themselves until they are bald. Some dogs also develop chronic digestive problems which are manifested in the form of diarrhoea, vomiting, flatulence and loss of appetite. If the respiratory tract is affected, this causes a sniffling nose, watery eyes, coughs, and asthma.