Allergy is increasingly common. Around 44% of adults in the UK have at least one form of allergy, and the number of people affected continues to grow.An allergic reaction takes place when your immune system mistakenly identifies a harmless substance as a threat, and takes excessive defensive action.Allergy symptoms can make you feel awful. It can make it difficult for you to function at work and affect daily activities with your friends and family. Ongoing allergy can also be linked to asthma.Allergy explained by GP Dr Sarah Glynne Your browser does not support the video tag.How do I know if I have an allergy?A big part of allergy diagnosis is the history of your symptoms. Doctors also use blood tests and skin prick tests, in which the immune system is exposed to suspected allergens in order to trigger a reaction.If you think that you may have allergy, or if you are not sure what causes your allergy, speak to your doctor to get an accurate diagnosis and find the right treatment for you. Understanding your condition will help you to manage your symptoms effectively.Types of allergyHay fever (allergic rhinitis)Allergic rhinitis – also known as hay fever – is an allergy to pollen and the most common allergy. Hay fever symptoms include frequent sneezing, a runny nose, and itchy eyes. Hay fever is triggered by pollen, released into the air by grass, trees and weeds. It affects both children and adults, with symptoms occurring mainly in the spring and summer.Your allergy symptoms may be particularly bad at a certain time of the day, when the type of pollen you are allergic to is at its highest. Weather also plays a role - more pollen is carried in the air on hot, dry and windy days.Find out more about Hay FeverHouse dust mite allergyDust mite allergy is a reaction to the waste produced by house dust mites, which can build up in bedding and cause particular problems overnight.The symptoms of house dust mite allergy are similar to those of hay fever and colds: blocked or runny nose, itchy or watery eyes, headache, tiredness in the morning, dry or sore throat, and coughing and sneezing. However, dust mite allergy can occur all year round, especially when you are spending more time indoors.Skin reactions and – in more severe cases – shortness of breath are also typical house dust allergy symptoms. House dust allergy sufferers are more frequently affected by asthma than people with other allergies.Read more about house dust mite allergyPet allergiesPet allergies are caused not by the animal hair itself, but by allergens of animal origin which are spread by animal hair, dander, and feathers. Animal hair allergy symptoms can be similar to those of hay fever – red or sore eyes, a runny nose and a tingling sensation in the eyes and nose. These symptoms usually occur shortly after contact with the allergen - either in the air or by touching an animal.Insect venom allergyBee and wasp stings can lead to life-threatening anaphylactic shock. Any symptoms that go beyond the normal sensation of pain, local redness and wheals should be taken very seriously. Those affected should see a doctor or call an ambulance as soon as possible.Food allergiesCow's milk, nuts, fish, shellfish and eggs are among many foods that can cause unpleasant allergic symptoms - from itching or nausea to anaphylaxis. Food allergy is different to food intolerance, which is where your body is unable to process certain foods.Find out more about food allergiesMould allergyA mould allergy is triggered by dead fragments or spores of moulds. Since moulds are found almost everywhere, the symptoms of mould allergy, such as runny nose, cough or even asthma often occur year-round.Latex allergyThe typical symptoms of a latex allergy are usually allergic skin reactions, such as redness and wheals, on the parts of the body that have come in contact with latex-containing materials. In severe cases, a latex allergy can also trigger anaphylactic shock.