An allergy appears when the immune system of the body has a reaction to allergens, or irritating substances in the environment. There are many different types of allergies and allergic diseases. An estimated 21 million adults in the UK suffer from at least one allergy and an estimated 10 million adults suffer from more than one.1
If your allergy only appears during certain periods of the year, you are having a seasonal allergy, but if it is causing problems all year around, your allergy is perennial. If you are unsure of what type of allergy you are having, it will be a good idea to see a doctor for a full allergy testing so that you will get the right treatment. Your symptoms, how serious your allergy is, and what type of allergy you have are factors that decide what medication will suit you the best.
Allergic symptoms that only appear during spring and summer is usually hay fever caused by pollen. Hay fever affects one in four people in the UK and is mainly caused by grass pollen.2 It has not been fully shown why some are affected by pollen allergies, but heredity is an important factor. Most often the allergy first appears during childhood.
Hay fever may cause your nose to run, sneezing, nasal congestion and irritated eyes. Many people with hay fever will also have asthmatic symptoms such as coughs and wheezing chest sounds, especially during days where there is a lot of pollen in the air. In some cases, people allergic to pollen develop allergies or hypersensitivity to certain foods. For example, nuts, apples, stone fruits, peaches and almonds. This is called oral allergy syndrome and is caused by a similarity in proteins from certain animals and plants. Oral allergic syndrome can lead to symptoms such as swollen lips as well as itchy throat and upper respiratory tract.
Perennial allergy is caused by hypersensitivity to pets or dust mites, and the symptoms may appear all year around. It often proves more difficult to diagnose perennial allergies, since other things may also cause prolonged nasal congestion, and it is not as easy to connect the symptoms and contact with the allergen. It might be necessary to perform an allergy test in order to find the cause.
The symptoms of perennial allergies are similar to those of pollen allergy, even though the nasal congestion is usually more severe in perennial allergies. Cat and dust mite allergens are small and move easily down into the lower respiratory tract, which may lead to asthma symptoms.
Food allergy is a hypersensitivity to certain foods and is especially common among children. Among young children, allergies to cow milk and eggs are the most common, while older children more often react to nuts and peanuts. Symptoms usually appear on the skin as eczema or nettle-rash, or come from the gastro-intestinal tract. Nausea, vomiting, constipation, an itchy mouth and swollen lips are symptoms that may be caused by a food allergy. In rare cases, food allergies or an allergy to bee and wasp stings lead to anaphylaxis, which is a life threatening condition causing acute breathing difficulties and a sudden fall in blood pressure.
Contact dermatitis is a type of allergy causing eczema through direct skin contact with an irritating substance.
1. https://www.allergyuk.org/allergy-statistics/allergy-statistics. Date accessed November 2015.
2. http://www.nhs.uk/conditions/hay-fever/Pages/Introduction.aspx. Date accessed November 2015.
UK/GEN/15/0057b Date of preparation: December 2015