Allergies are a reaction in the immune system to things your body thinks is harmful but really isn't.
Substances that cause allergic reactions have been known to be certain foods, dust, plant pollen, or medicines. Airborne particles that can cause allergies include dust mites, mold spores, animal dander, and pollen from grass, ragweed, and trees.
Allergies can have all types of symptoms depending what you are allergic to. Symptoms have been know to be an itchy rash, tingly tongue, diarrhea, hives, and an anaphylactic reaction. Some symptoms can be mild like a runny nose or have a difficult time breathing.
The best way to avoid allergic reactions is to never be near the thing that causes them. Avoidance can protect people against non-food or chemical allergens too. If you are allergic to airborne particles, keep windows closed, change clothes after going outside, and don't mow lawns, avoid damp areas like basements and keep bathrooms and other rooms clean and dry.
If your are severely allergic many will need to have a shot of epinephrine which is a fast-acting medicine that can offset an anaphylactic reaction and it comes in an easy-to-carry container that looks like a large pen. There is also an allergy shot or sometimes referred to as allergen immunotherapy which gives you small injections of an allergen, but this is only recommended for specific allergies such as airborne particles or insect allergies. This can raise a person's tolerance when exposed to the allergen which means fewer or less serious symptoms.