How do you know the rash is hives? If the rash comes and goes within 24 hours, it is most likely hives. But hives can either be acute or chronic. The two types share many common triggers. The big difference is timing. For acute hives, you’re just dealing with one bout of hives, or they may come and go, but they resolve within six weeks. If you have chronic hives, the rashes continue to appear and disappear for longer than six weeks. In these cases it may be tougher to pinpoint a cause. Here’s more on common triggers and what happens in the body that leads to hives. To understand the basics, it helps to know a little bit about the body’s allergic response. Your body produces mast cells, which act as part of your allergic response. (2) When your body perceives it’s been exposed to a threat, the mast cells may secrete numerous chemicals, most notably histamine, explains Sarina Elmariah, MD, PhD, a board-certified dermatologist at Mass General Brigham in Boston. In most situations, histamine causes your blood vessels to dilate and leak fluid, creating the raised areas on your skin (hives). Histamine also affects your nerve cells, signaling your skin to itch, Dr. Elmariah says. A lot of people assume that hives are the result of the release of histamine, a chemical your body produces in response to allergens. Histamine does play a role in the majority of cases, but it’s important to know it can be more complex than that, Elmariah explains. “Some hives are beyond the scope of histamine and involve other chemicals.” In other situations, basophils, another type of white blood cell, may be activated to release their hive-producing chemicals and cause the same effect, Elmariah says. If you’re allergic to things like insects, medications, latex, or certain foods and you come in contact with your allergen, a protein found throughout the blood and body tissues called immunoglobulin E (IgE) will bind the allergen and signal the mast cells to release their contents, histamine included, Elmariah says. RELATED: Common Allergy Symptoms and Triggers Hives may also result when other blood protein antibodies (besides IgE) bind directly onto mast cells, prompting them to release their contents, or in other situations, mast cells may be completely degranulated or destabilized, which induces the chemical release, Elmariah says. Fortunately, although hives can be extremely itchy, they’re not contagious, and an individual hive usually disappears within 24 hours, Elmariah says. (If a single hive lasts for longer than 24 hours, the cause could be more serious and you should call your doctor.) For some people, hives can be so chronic in nature (with single hives coming and disappearing continuously) that they can be an issue for months. (3) Hives can even be so problematic that they interrupt healthy sleep, work, and school and isolate people socially, affecting mental as well as physical health, Elmariah says. But some triggers are more common than others, and the three at the top of the list are food, drugs, and infections.
Foods That Trigger Hives
Hives from food are usually related to food allergies, especially fish, shellfish, and peanuts. You may even have hives as a result of a pseudoallergic reaction, a reaction to a food or chemical that mimics the symptoms of an allergic reaction, but without IgE antibodies being produced against the offending item. (4) Pseudoallergic reaction triggers can include artificial food dyes, tomatoes, preservatives, sweeteners, herbs, wine, high dietary fats, alcohol, salicylic acid, orange oil, strawberries, and yellow and red food dyes.
Drugs That Trigger Hives
On the drug front, there are several that can cause hives, including nonsteroidal anti-inflammatory drugs (NSAIDs), aspirin, muscle relaxants, antibiotics, diuretics, IV radiocontrast, ACE inhibitors, and angiotensin receptor blockers, explains Anthony M. Rossi, MD, an assistant attending dermatologist at Memorial Sloan Kettering Cancer Center in New York City.
Infections That Trigger Hives
Infections might include viral ones like the common cold and hepatitis or bacterial ones like strep throat or urinary tract infections, Dr. Rossi says.
Other Things That Trigger Hives
You can also get hives from touching things you may be allergic to. For instance, if you’re allergic to latex, you might get a hive if you touch a balloon or latex glove. The same is the case if you’re allergic to dogs and a dog licks you. Other things that can cause hives include blood transfusions, insect bites or stings, plants (like nettle, also called stinging nettle), and to a smaller degree, stress (usually it takes emotional stress combined with some other factor to trigger hives, rather than emotional stress triggering hives on its own). Environmental stimuli may cause hives, something experts call inducible urticaria (often referred to as physical urticaria). Things like pressure on your skin, exercise, changes in your body temperature, sweating, cold, heat, water, sun exposure, and vibrations can instigate an episode of hives. “You might simply be walking by a construction site or riding a train, and because of the vibrations from these things, you break out,” Elmariah says. These types of hives occur less frequently than those caused by food, drugs, or infections. Chronic hives, meanwhile, can be caused by any of the above, but they may also be a sign of a health issue or autoimmune disease. “Autoimmune diseases in general have been strongly associated with the development of chronic hives,” Elmariah says. Yet some have a stronger link to hives, such as thyroid disease, type 1 diabetes, celiac disease, lupus, and rheumatoid arthritis. (5) If your throat starts to swell or you’re having trouble breathing, seek emergency care immediately. If hives appear to come and go for longer than six weeks, they’re considered chronic, and it’s best to visit a dermatologist to see what’s going on, Rossi adds. The caveat? “Although hives in and of themselves generally aren’t life-threatening, they can be associated with a condition called angioedema and a severe allergic reaction known as anaphylaxis, both of which can cause breathing issues and require emergency care,” Elmariah explains. Forty to 50 percent of hives cases are associated with angioedema, (4) which involves swelling of the eyes, mouth, hands, feet, or throat. It can be caused by medications, allergic reactions, or a hereditary deficiency of some enzymes in your body. (7) Meanwhile, anaphylaxis can result if you’ve been exposed to something you’re allergic to, especially if that allergy is severe. Emergency visits aside, when you do see your doctor to determine what’s causing your hives, come prepared with information. Here’s what Elmariah recommends having on hand:
Any trigger you’ve identified, including foods, chemicals, medication exposures, even travel historyA list of all your current or recent medicationsYour medical history, including other personal and family history of medical problemsA list of medications (and doses) you’ve already tried and the effects they’ve had
Hives may be an annoying condition, but with the right medical attention, you can learn how to manage them and, in many cases, prevent them from happening again.
