What are hives?

Many folks, allergic or not, have had the experience of breaking out in hives. A hive is a raised, typically flat or slightly domed area of skin that is red, feels hot and usually itches. Hives may be coin-sized and round or they may be quite large with irregular borders. Typically an individual hive lasts for a few hours before disappearing, but it may occasionally last an entire day or longer. Normally, when hives resolve they leave behind normal unblemished skin. Though they are itchy, scratching doesn’t help. In fact, many folks with hives find that scratching just brings up more hives! The medical term for hives is “urticaria.”

Why do we get hives?

Where does this annoying and at times disfiguring rash come from? Most commonly, a hive results from the local release (in the skin) of a chemical made by our own cells called histamine. This is the chemical that causes itch and swelling wherever it appears. If that’s in the lining of the nose, it causes sneezing and congestion; if it’s in the lining of the eyes, it can cause intense itch and puffiness. When it is released in the skin, the result is a hive (or multiple hives if the histamine is released at more than one location).

So why do people with hives have histamine being released in their skin? Unfortunately we don’t always know the answer to that. A sudden attack of hives (without having had them before) is frequently triggered by exposure to something to which we are allergic. The trigger may be a food, medication, or even a venom (for example from a bee sting). The first time this happens, we don’t usually know we’re allergic (or we would have avoided that trigger!) Therefore, one of the tasks in evaluating new hives, along with trying to control them, is to identify the culprit trigger. An attack of hives resulting from an allergic trigger can be short lived (hours) or may persist for several days. Once the episode resolves, the hives don’t reappear until we are exposed to the allergic trigger again (this may be weeks, months or even years). In this situation, each outbreak of hives is referred to as an “acute” episode.

Persistent Hives

Acute hives contrasts with another form of this rash in which the annoying itchy bumps appear daily, or nearly daily for extended periods (weeks to months). When hives persist with minimal relief for more than six weeks, they are referred to as “chronic”. In contrast to acute hives, the chronic form typically does not result from exposure to an allergen. This syndrome is still not well understood, but the rash of chronic urticaria appears to result from biochemical processes within our own bodies rather than from external triggers. Sometimes a viral infection may set this process in motion, but more often than not, no clear cause is identified. It’s still worth paying attention to what you are eating and what medications may have been started recently, because occasionally an environmental trigger may turn up. However, if you are experiencing chronic hives, don’t be frustrated if you can’t come up with a trigger – in most cases there is no obvious one.

What can I do?

If you are experiencing your first episode of hives, you should think back to when they first appeared and consider what might have been the trigger. Write down for future reference where you were during the 12 hours before they appeared, what you were doing, what foods or medications if any you ingested, whether you felt healthy or were fighting an infection. Be as detailed as you can. This information is crucial to narrowing down the list of potential triggers and possibly giving your allergist the opportunity to test you for allergy to some of them.

Keep in mind that if this is an allergy you were not previously aware of, the hives could come back if you get exposed again at a later date. If that happens, don’t despair. Make yourself go through the same process of writing down the “wheres, whens, and whats” of the 12 hours before the hives started. You may not immediately identify an obvious trigger, but your allergist may be able to find a pattern in your outbreaks that doesn’t occur to you. For this reason, these written accounts, recorded while your memory of the events is fresh, can make the difference between identifying a trigger rapidly and not.

If you have been suffering with hives for a more extended period (with little relief for 4-6 weeks or longer) you’ve probably already spent a fair amount of time trying to identify a trigger, and without much success. Your allergist will still want to review the “wheres, whens, and whats” leading up to the appearance of the hives. But it will also be important to check some basic blood tests to look for identifiable and treatable health conditions that can result in hives. If these tests are all normal (as they are in most cases), the goal shifts from identifying a cause, to controlling the symptoms. You and your allergist will work together to find a treatment approach that allows you to be as free as possible from the hives while minimizing the inconvenience and side effects of taking medication. The good news is that the vast majority of chronic hives episodes resolve as mysteriously as they appeared. As uncomfortable (and disfiguring) as this rash may feel, you should take heart that this condition is actually quite common and the outbreaks are typically self-limited without long term implications for your health.

More Resources

For more information on hives, please see the following: