Hives (Urticaria)

Hives are non-infectious itchy raised welts with an endless list of causes. This common skin rash, also known as urticaria (ur-tih-kar-e-uh), is usually initiated by some type of irritant. It is a frequent mistake to believe these inflamed patches are always due to an allergic reaction. Although an allergy is often responsible for the presence of hives, they can also occur from tight clothing, sun exposure, or anything that aggravates the skin.  

Foods, medications, or even stress are a few reasons you might find yourself with itchy patches of inflammation. Often, the source remains unknown, especially in chronic or long-term cases. Whatever the basis is for your hives, they can be uncomfortable but are rarely dangerous and usually resolve on their own.  

Presentation varies widely. You might notice a small patch on your arm, or to your surprise, it engulfs your entire body. Hives can even show up on your lips or in your throat. They may appear suddenly without any clue why, or the origin may be obvious after becoming itchy whenever you pet the neighbor's cat. Whatever the cause, they can be annoying but are usually harmless.  

The Physiological Process of Hives 

Hives, or urticaria, occur when blood vessels dilate and leak fluid into the skin. The fluid leakage is in response to histamines and other substances released by activated white blood cells found in connective tissue. These specialized white blood cells, called mast cells, are found throughout the body but are particularly fond of hanging out under the skin.  

Mast cells play an essential role in your immune system by attacking infectious microbes with a swift response. These multifaceted cells fight off pathogens in more than one way. They release chemicals toxic to foreign invaders and dilate blood vessels so additional white blood cells can readily travel to the infection site.i 

Sometimes mast cells become overly sensitive and react to more than just infectious intruders. Just about anything can activate susceptible mast cells. Scratching your skin when it tickles or pressure from carrying heavy bags over your shoulder can excite them enough to release histamines and cause hives. Hypersensitive mast cells react to just about anything, including tight or scratchy clothes, heat, cold, sweat, allergens, or even stress. 

Hives vary from mild to severe and can emerge, fade randomly, and return without warning. You may see just one or two, or your entire body could become consumed. The inflammation can last just a few minutes or several days. In the case of chronic hives, they stick around most days of the week, coming and going for months or years.  

Hives appear as multiple patches of inflamed, red, or purple skin and can arise anywhere on the body. The patches vary in size and tend to be itchy, with some patients describing them as painful. Anything that aggravates the skin can result in a flare-up. Contact a physician if your hives are severe, covering a large portion of your body, or last more than a few days.  

Many believe hives are a dangerous allergic response, but that is not the case. However, they can be associated with a serious allergic reaction called anaphylaxis. If you go into anaphylaxis, there is a good chance you will have hives, but if you have hives, that does not mean you will progress into an anaphylactic reaction.  

Symptoms of anaphylaxis include skin responses like hives, flushing, itching, or pallor (pale skin). You may begin wheezing, struggle to breathe, or lose consciousness. You may also feel dizzy, sweaty, confused, and anxious. An anaphylactic reaction can lead to anaphylactic shock, where your blood pressure drops so low your cells and organs become oxygen starved. Anaphylactic reactions are considered medical emergencies.  

Most people never pinpoint the source, and in many cases, it is unnecessary anyway. Hives often erupt suddenly and clear just as quick as they appeared, never to bug you again. However, if they are persistent, severe, or frequently bothersome, finding a cause can be critical for your comfort.  

Environmental Stimuli 

Some people release histamines and develop hives from physical or environmental stimulation to their skin. If you have this condition, stimuli like hot or cold temperatures, pressure against the skin, exercise, sunlight, or even water may lead to uncomfortable and itchy skin. This type of urticaria is called inducible or physical urticaria.  

Allergies 

Localized allergic hives are usually due to your skin contacting a trigger, like a patch on your ankle where the dog licked you. Widespread allergic hives are more likely due to an allergic reaction to an ingested food or medication. Sometimes the cause is apparent. However, you may need to undergo testing if you cannot identify a reason for your rash.  

Hives resulting from an allergy require you to find your triggers and avoid them. Your doctor can order specific blood tests or allergy skin testing to discover the culprit. A blood test looks for antibodies your immune system produces specifically to common allergens. A skin test exposes your skin to known allergies, followed by an examination to look for reactions.  

Autoimmune Diseases 

If your hives are chronic, your doctor may want to investigate the possibility of an autoimmune disease. Autoimmune diseases are conditions in which your immune system attacks healthy tissue mistaking it as foreign and can lead to skin reactions. You may need to provide a blood sample for laboratory testing, so your healthcare provider can gather information about your overall health.  

Drug Reactions 

Allergic reactions to medicines can occur with any drug, including herbal supplements. If you experience hives after ingesting medications, there is a possibility it is due to an allergy. Drug allergies can generate severe and life-threatening reactions. If you break out in a rash after taking medication, even if symptoms are minimal, contact your doctor. If you experience a severe reaction, seek immediate medical help. 

Viral or Bacterial Infections 

Viral infections are a common cause of hives, especially in children. In one study evaluating urticaria in kids between the ages of 1 and 19, almost half with acute urticaria had a documented infection. During an illness, the immune system can become overly excited about fighting off a pathogen and signals for mast cells to release histamines.  

Types of Hives 

Hives come in different varieties and different classifications. There are two main types, acute and chronic. Grouping them into categories allows for a more straightforward diagnosis and treatment. If your doctor knows what kind you have, they can tailor a plan to manage your condition.  

Acute Urticaria 

Acute urticaria, or acute hives, last six weeks or less, appears suddenly, and often passes without trouble. This type is usually due to an allergy or infection. You might experience acute hives when something you are allergic to contacts your skin or from ingesting certain foods or medicines. Certain pathogens, usually viruses, can also make your skin breakout.    

Chronic Urticaria 

When your hives last longer than six weeks, they shift away from acute and move into the chronic category. Chronic urticaria can flare up daily and may last months or even years. Most cases exist without a known cause.  

Chronic urticaria is broken down into two main types, inducible and spontaneous. Inducible chronic hives are initiated by physical stimuli like heat, pressure, or sun exposure. If your hives are not inducible, they are considered spontaneous.  

Chronic urticaria can result from an autoimmune disease or long-term infection. However, if there is no identifiable cause, you have chronic spontaneous urticaria. Most cases remain a mystery with no known cause.  

Inducible (or Physical) Urticaria 

Inducible urticaria is a type of chronic urticaria that occurs from environmental stimulation of the skin and comes in several different forms. The kinds of inducible urticaria are:

• Dermographism  

• Exercise-Induced  

• Delayed-pressure  

• Cold  

•      Cholinergic  

• Aquagenic  

• Solar 

Dermographism is a type of urticaria that occurs when the skin breaks out in hives after being scratched, stroked, or mechanically irritated. Irritation from scratchy clothing or even a slight scratch from bumping your arm can result in red and aggravated skin.  

Exercise-induced urticaria occurs after physical exertion, sweating, or sustained activity. It usually comes on suddenly and resolves quickly. In severe cases, exercise-induced anaphylaxis can occur.  

Delayed-pressure urticaria is characterized by eruptions of hives after sustained pressure on the skin. Your hands, soles of your feet, buttocks, and areas under tight belts or bra straps are most frequently affected.  

Cold-induced urticaria is a skin reaction to cold exposure. Welts can be mild to severe and appear within minutes after exposure. You may notice hives on your hands after holding cold items or swelling of your lips when you consume cold food or drink. Even cold air can lead to eruptions.  

Cholinergic urticaria is a rash associated with an increase in body temperature. Anything that raises your temperature can cause hives with this type of urticaria. Fevers, feeling anxious, or taking a hot bath can trigger your body to release histamines, resulting in hives.   

Aquagenic urticaria is an extremely rare form of hives where your skin reacts to water regardless of temperature or source. Rain, showers, swimming, or even touching water to wash your hands can stimulate hypersensitive mast cells and irritate your skin. As of 2018, only 50 cases have been reported in the medical literature.vi 

Solar Urticaria is a rare photosensitivity disorder where your skin reacts to sun exposure. The reaction is usually sudden and can appear from just a few minutes in the sun. In more severe cases, the hives can turn into blisters.  

Chronic Spontaneous Urticaria 

Chronic spontaneous urticaria is a condition in which you experience hives lasting beyond six weeks with no identifiable etiology or known cause. You may, however, detect circumstances that aggravate your symptoms. The rash can come and go daily but exists most days of the week. Although eruptions can appear anywhere on your body, you'll likely observe specific areas that tend to be more affected.  

There are no laboratory or clinical tests available to diagnose this condition. Your doctor must rely on signs and symptoms while eliminating other potential causes to reach a diagnosis. Once diagnosed, your doctor can help you manage your hives even without knowing the origin. In 80% of cases, symptoms resolve without treatment within two to five years.

Angioedema Versus Hives 

Urticaria and angioedema share similar triggers and occur together in 49% of cases. They are both an overreaction of the immune system and are usually self-limited. Although there are many commonalities between urticaria and angioedema, they present differently.  

Hives affect the superficial layers of the skin with itchy welts that have a rash-like appearance and somewhat clear borders. Angioedema involves deeper layers of skin and presents as localized tissue swelling. Angioedema is rarely itchy but can burn and feel uncomfortable, which is also sometimes seen with hives.  

Angioedema can affect anywhere on the body, including your intestines. If your intestines are involved, you may notice digestive problems like abdominal pain, diarrhea, nausea, and vomiting. You can also suffer from swelling in your hands, feet, genitals, or face, including your lips and tongue. In severe cases, you may feel dizzy or faint due to changes in blood pressure.  

Swelling in your tongue or throat can obstruct your airways and make breathing difficult. Seek immediate medical attention if your angioedema affects your ability to breathe. If you feel dizzy, lose conciseness, or have difficulty breathing, it is a medical emergency. Call 911 or go to the nearest emergency department straight away.  

A physician can usually diagnose hives after a brief medical history and visual inspection of your skin. However, finding the reason behind them will require more digging. At your consultation, plan on answering questions about your diet, medical history, potential triggers, and medications you're taking. Little details may be the key to discovering why your skin is reactive.  

In preparation for your appointment, document when your welts first appeared and all associated signs and symptoms. Take pictures in case your skin improves before your scheduled appointment, and write down any questions you want to ask. Make a comprehensive list of your medications, including prescription and over-the-counter. Include vitamins and supplements.  

Depending on severity and frequency, your doctor may order laboratory testing to look for allergies and other conditions that produce hives. You might need to have your blood drawn or undergo an allergy skin test. Identifying and treating the cause will reduce your symptoms.  

In many instances, a cause is never uncovered. Fortunately, eruptions usually calm down within a few days, even when you don't know what provoked them. If your doctor cannot determine the root cause of your rash, they can still offer treatment options to help ease discomfort as you wait for symptoms to recede.  

Treatment will vary based on the cause and severity. If your rash is mild, you can apply over-the-counter anti-itch cream or wait for it to improve without intervention. In most cases, hives and angioedema settle on their own. Schedule an appointment with your doctor if your symptoms are bothersome.  

Depending on the cause, you may be able to identify and avoid triggers. If you find you are allergic to a particular food or medication, avoidance will be your best option. Your doctor may prescribe you an auto-injectable epinephrine delivery device if your reactions are severe. Injectable epinephrine is a life-saving medication administered in the event of an anaphylactic reaction.   

If you have an underlying condition causing your hives, treating it will improve your symptoms. The diagnostic process may require laboratory testing and can take time. Be patient and work with your doctor as they figure out the best way to manage your situation. In the meantime, you can take medication to ease your hives while you wait for a diagnosis.  

With inducible urticaria, a multipronged approach of avoidance and medications can improve your symptoms. Avoid or limit your known triggers whenever possible. If your hives show up every time you wear jeans, switch to softer materials. Making minor adjustments may be all you need to keep your hives under control. If you are still uncomfortable, your doctor can prescribe medication.   

Sometimes even when you do your best to control hives, they prevail. But the battle is not lost. Your doctor may recommend over-the-counter antihistamines or give you a prescription. Antihistamines work best to prevent hives when taken routinely. However, you can still take them as needed in response to acute flare ups. If antihistamines don't offer relief, your doctor can prescribe an oral steroid.   

Hives come in a wide variety and show up for many reasons. It is tempting to analyze every detail of what you touched, ate, or looked at in the hours leading up to your hives, but that level of scrutiny is unnecessary. In most cases, you can ignore this self-limiting rash and carry on with your life while you wait for it to pass.  

Contact a doctor if your symptoms are excessively bothersome or last longer than a few days. Our licensed physicians can help you decide the best way to manage your condition and get you back to your everyday activities. Even if your hives are minimal and brief, we are happy to help answer your questions.  

Our qualified doctors can provide accurate information and help you decide the best course of action. We understand that although hives are generally not dangerous, they can still be worrisome. If you have concerns, big or small, we are happy to help.