Hives are typically red, raised bumps or welts on the skin that can occur anywhere on the body. They are normally very itchy and may come and go for several hours or days once they appear. Hives often appear as reaction to an allergen.
Hives occur when the chemical histamine is released into the blood stream. Histamine causes the small blood vessels in the skin to become “leaky” allowing areas of swelling or raised bumps. If the leaky vessels are deeper in the skin (lips, eyes, ears), this may result in more significant swelling.
Allergists often divide hives into two categories: acute (occurring for 6 weeks or less) and chronic (occurring for 6 weeks or more). Acute hives are commonly caused by exposure to an allergic trigger. By reviewing your history thoroughly, your allergist can help to narrow down the cause so that the exposure can be avoided and, thus, the hives avoided. This may require the use of skin testing in which a small amount of dilute extract containing pollen, animal dander, food protein, etc. is placed on the skin followed by a light puncture or scratch. Within 15 minutes, a positive reaction (similar to a mosquito bite) may appear.
Chronic hives, on the other hand, are usually not from an allergic reaction. An evaluation for chronic hives may also include skin testing and some blood tests. Your allergist will work with you to determine a medication regimen to control the hives when they are present.
An allergy is the result of the immune system overreacting to a substance that is typically harmless, such as plant pollen or animal dander. This overreaction causes the release of chemicals, including histamine, into the bloodstream and may result in runny nose, sneezing, itching, nasal congestion and cough.
Having a family history of allergies seems to be the main reason that people develop allergies. If both parents have allergies, their child has a 75% chance of being allergic. If only one parent has allergies, their child has a 30 – 40% chance of developing some form of allergy. If neither parent has allergies, a child still has a 15% chance of developing allergies. Although children are more likely to develop allergies, anyone may develop an allergy at any age. Approximately 50 million people in the United States suffer from allergies; of these, at least 9 million have asthma.
With the use of skin testing, specific allergens can be identified. For the testing, a small amount of diluted extract containing pollen, animal dander, mold, etc. is placed on the skin, followed by a light puncture or scratch. Within 15 minutes, a positive reaction (similar to a mosquito bite) may appear. This information can be used to develop a specified treatment plan including avoidance measures, medication and possibly allergy shots.