As an allergist, exploring the reason a particular patient has recurrent hives makes me really feel like a detective. For many conditions that an allergist sees, patients usually have a general idea of what may be causing their symptoms. However, for chronic hives (also known as urticaria), there is usually no particular consistent pattern or trigger, and the sufferer remains baffled.
First, let’s be sure we are all on the same page regarding what hives are. They are usually reddish bumps that can range in size from very small to very large. They are usually intensely itchy and can occur on all parts of the body, including the bottoms of the feet, palms of the hand, and even the scalp. They can last for just a few minutes or for several hours before disappearing, sometimes, without a trace. On occasion, along with the hives, random swelling of different body parts can also occur, such as a hand, an eyelid, or a half of one’s face.
Here is a patient you may relate to:
A man in his late 40s has been having seemingly random episodes of hives for the past two months. The hives appear on different parts of his body almost daily. They last for a few hours at time. The last time he had hives was about two days ago and he also had some swelling of his upper lip, which was new. He took some Benadryl and the swelling went away within the day. The hives seem to appear at any time of the day or night. He has not had any new foods or medications, or any recent changes in his life. He is otherwise healthy. He admits to having a lot of stress at work lately, but he has not had any other changes in his life. He suspected that the hives and swelling might be that he was allergic to something he was eating in his diet, so he concluded that he must have developed an allergy to dairy products as it is the thing that he ingests almost daily. He stopped eating dairy for the past two weeks, but the hives continued. He’s having trouble sleeping at night due to the itching and having trouble focusing at work because the daytime itching is unbearable and distracting.
When considering the possible causes of an individual’s hives, it helps to think about three broad groups of causes:
1) An allergic reaction– This could be a reaction to many possible culprits such as medications, foods, spices, preservatives, skin care products, detergents, pollens, animal dander, etc. Keep in mind however that whatever the allergen is, in order for it to be the cause of symptoms that have lasted over the course of several weeks or months, it will likely be something less obvious and something that you would likely be exposed to frequently. It would be unlikely to be exposed to something weeks ago that would still be causing the hives you had today. To figure this out, consider a keeping a journal of your exposures and your symptoms to help identify any patterns that may be there. Once the hives become chronic, meaning that they have been happening for 6 weeks or more, this becomes the least likely reason a person would have hives.
2) An underlying condition or disease process– Hives can be a result of an abnormal response of your immune system to some other seemingly unrelated illness going on in your body. For example, some conditions like lupus, thyroid disease, or even cancer can be related to chronic hives and swelling episodes. It’s important that when discuss your symptoms with your doctor that you let them know about any other issues that you have noticed with health. Your doctor should also perform some testing to look for some of these conditions when appropriate.
3) Idiopathic –This means that we don’t really know what caused the hives initially. As a doctor, I don’t like to say “I don’t know”, but in the case of chronic hives, I have to say this more often than not. This is by far the most common determination after ruling out other causes. However, just because we may not know the underlying cause, it does not mean we don’t understand the underlying mechanisms of the condition and how to treat it. Additionally, understanding triggers for the hives and swelling episodes is also important even if the underlying cause eludes us. Some common triggers can include trauma, stress, infections, and extremes in temperature, exercise, and physical pressure, among others.
In the case of our patient above, after testing to rule out allergic causes and possible underlying conditions, it was determined that he had the idiopathic form. His symptoms were controlled with a combination of medications and minimizing his triggers as much as possible.
The good news about hives is that they can be successfully managed after a thorough evaluation and in many cases they can resolve over time.
Allergies Demystified 