An estimated 50 million people in the United States suffer from allergies – everything from dust mites to smoke. Many of these are seasonal allergies and don't really have any serious or long term effects, although an estimated 32 million people suffer from what are known as year-round chronic allergies.

The symptoms of allergies can vary from mild to severe; and can include coughing or sneezing, a runny nose, sore throat, rash or headaches. Many allergy sufferers regard their symptoms as a minor irritation; to others the symptoms are serious enough to keep them off school or work and to require medical help. An allergy can be triggered by eating or drinking, inhaling or touching.

The most common allergies fall into two basic types – airborne and food allergies. The most common food allergies among adults are nuts, shellfish, eggs and fish – children are more likely to be allergic to peanuts and dairy products. In fact, only eight foods account for around 90% of all allergic reactions to food.

Food allergies occur when the body's immune system reacts to a certain food, often creating antibodies which then release various chemicals which in turn cause the symptoms. Avoiding the food altogether is really the only sure way to avoid an allergic reaction, although this is often impractical; and you also run the risk of suffering from an unhealthy diet.

Symptoms of food allergies range from mild to extreme – even a loss of consciousness and death. Some common symptoms can include swelling of the skin, hives or eczema, as well as stomach pain, vomiting or diarrhea. An extreme allergic reaction to food is known as anaphylaxis, or anaphylactic shock, which can lead to low blood pressure, difficulty breathing and unconsciousness.

Skin allergies are caused by actual contact with an allergen, rather than inhaling it or digesting it. Metal jewelry and fragrances are the most common causes of skin allergy; other causes include such everyday things as soap, deodorant, various dental products and skin lotions. Symptoms are usually highly visible on the skin and can include swelling, burning, itching or redness of the skin – eczema, hives and dermatitis are all types of skin allergy. Dog allergies are surprisingly common, and can be difficult to control, as the allergens can be found in many public places. Many people find that they are more allergic to certain dog breeds than others. If you are allergic to dogs but enjoy having a dog yourself, there are some steps you can take such as keeping it in an area of the house that isn't carpeted, bathing your dog regularly, making sure it is neutered and using a HEPA room air cleaner.

Common symptoms of dog allergies include nasal congestion, coughing, watery or itchy eyes, and shortness of breath or a runny nose. Extreme symptoms can include a rash on the face or upper part of the chest, or an acute asthma attack. These symptoms can occur within about thirty minutes of contact with a dog, or they may not be noticeable until several hours later.