What are Hives?
Hives (urticaria) are raised, red areas of skin that itch and appear as lumps or weals with defined edges. They vary in size, from a few millimeters to many centimeters and cover part or all of the body.
The color of hives varies from red through to skin colored and appear white when you press on them (blanching). They can also “move” around the body, disappearing from one place only to reappear in another.
This condition is thought to affect up to 20 percent of the population at one time or another. Hives can be acute, lasting anything from a few days to a few weeks, or chronic lasting more than six weeks. (1)
Hives can be triggered by many things and are generally an allergic reaction. However some of the causes can also be down to physical repercussions.
Foods often generate an allergic reaction which can have several unpleasant effects. A severe food allergy can induce a response which affects more than one part of the body. (2)
There are many foods that cause an adverse reaction in the body. The main culprits are cows milk, eggs, walnuts, hazelnuts, peanuts and shellfish. One of the symptoms of food allergies is hives. (3)
Insect Bites and Stings
When we get bitten or stung our immune system defends us against foreign substances injected into the skin. It produces antibodies to deal with what it deems harmful to us.
There are instances when this can set off an allergic reaction in our body and one sign of this is hives. (4)
Sometimes medication we take to treat various illnesses and conditions can cause an allergic reaction. Some of the drugs responsible include aspirin, antibiotics, non-steroidal anti-inflammatories, anaesthetic muscle relaxants and opiates.
The reaction can be immediate or take several days to manifest and can be mild through to severe. Hives are one of the symptoms of drug allergies. (5)
Pet allergies are common, as many as one out of ten people can attribute allergic reactions to household pets. Other animals like horses and cattle can also be responsible.
Popular belief is that pet hair causes this response, however it’s attributable to urine, saliva and dander (dead skin cells). These, along with dust and pollen are found in the fur and cause hives as part of the allergic reaction. (6,7)
Particles that we breathe in from the air around us can result in allergic reactions and cause hives. These include pollen and dust mites. (8)
The natural sap produced by the rubber tree is called latex and is used to make natural rubber. It is found in many thousands of industrial products, about 400 of which are medical.
Contact with latex products can produce many allergic reactions including hives. Things which have been handled by people wearing latex gloves can also produce reactions. (9)
Bacterial and Viral Infections
Many bacterial and viral infections can cause a reaction which will produce hives. These include streptococcus and staphylococcus infections, hepatitis, influenza, tonsillitis and urinary tract infections. (10)
Cold weather or swimming in a cold pool can have a detrimental effect on some people. Hives can appear within a couple of minutes of exposure and can last for about one to two hours.
This generally happens when the skin is exposed to temperatures below 39℉ (4℃) . In about half of cases people with this condition will improve within five to six years. However for some this rare condition can be a lifelong affliction. (11)
A rise in the body’s core temperature can produce sweating which causes hives. This is called cholinergic urticaria and is more commonly referred to as heat rash. The appearance of the hives will generally be about 2-4 mm in size.
It can be induced by exercise, fever, hot baths or showers, watertight dressings, eating spicy food or stress. (12)
Exercise can induce two types of hives. Those associated with heat of which we have already discussed and a more serious anaphylactic reaction.
The more serious condition produces hives about 10 to 15 mm in size and is accompanied by feelings of warmth and flushing. It generally happens when exercise is strenuous and may need immediate treatment. (13)
The sun and certain artificial UV lighting can cause photosensitive reactions in some people. Hives appear in areas of the skin exposed to the sun and elsewhere on the body. (14)
Wearing tight clothes or shoes can cause hives to appear in the areas where pressure has been applied. This is called dermographism and and may appear immediately or sometime after the pressure has been removed. (15)
There are a few other things that can cause hives like coming into contact with poison ivy or nettles. It can also be associated with some illnesses, changes in hormone levels and stress. Certain chemicals, perfumes, make up and other cosmetic products can produce allergic reactions. (16)
Hives itch profusely and can appear anywhere on the body including the face, arms, legs, back or abdomen. They are raised lumps or swollen marks that vary in size from a few millimeters to several centimeters.
They can appear to move around the body, disappearing from one location and coming back in another. When a hive is pressed the skin will look white and then the hive will reappear.
An individual hive will normally fade in about 24 hours and the skin will appear normal with no marks or bruising. Short-lived (acute) hives don’t last beyond about a six week period. Long-term (chronic) hives can appear daily and last longer than six weeks.
If swelling of the throat or any other symptom occurs that interferes with breathing immediate emergency care is needed. (17,18)
Doctors will generally follow a three step approach for allergy diagnosis to determine the cause of hives.
Personal and Medical History
To try and understand your symptoms and find their cause your doctor will ask many questions. They will want to know your family history and any medications you may be taking. They will want to know about your lifestyle and the foods you eat.
Sometimes the cause of the reaction may be obvious, like contact with something you know you have an allergy to. Other times you and your doctor will need to investigate further to identify a possible cause. However, there are times when the cause may remain unknown. (19)
Allergies often affect your ears, nose, throat, eyes, chest and skin. Particular attention will be paid to these areas during the examination. You could be asked to do a lung function test or you may even need x-rays.
As the main cause of hives is because of an allergic reaction there are tests that can be done to find out what you are sensitive to.
The skin prick test will involve a small amount of an allergen being put on your skin. It will then be pricked with a needle allowing the allergen to pass through the broken skin. Reaction, in the form of redness or a hive, will usually appear within 15 minutes if an allergy is present.
An intradermal skin test is similar to a skin prick test but involves the allergen being injected into the skin.
Blood tests can also be used to detect allergies. They can be added to blood in a laboratory to see if the blood produces antibodies against certain allergens. Whilst not as accurate, this test can be done when skin prick testing is not a viable option.
Physician supervised challenge tests involve a small amount of an allergen being inhaled or taken by mouth. Usually done for medication or food allergies, this test needs supervision in case of adverse reactions. (20)
What are hives? Hives (urticaria) are raised, red areas of skin that itch and appear as lumps or weals with defined edges. They are all different sizes, from a few millimeters to many centimeters and cover part or all of the body.
What causes hives? The main cause of hives is an allergic reaction to something like food, medications, insect bites, stings or animals. There are also physical causes like exercise, cold, heat and sun.
How do doctors test for hives? There are several tests doctors can do to see if you have an allergy and identify the particular cause. These could be blood tests or tests where the allergen is introduced into body through the skin, nose or mouth.
When should you go to the doctors with hives? You should see your doctor if your hives are still present after a couple of days. Recurring hives, a spreading rash, fever and swelling are also indicators you need medical help. Signs of anaphylactic shock include difficulty breathing or swallowing, fainting or dizziness and rapid severe swelling in the throat, face or mouth. If any of these happen then it is a medical emergency which needs immediate treatment.
Can you prevent hives? If you know what triggers your hives then by avoiding it or limiting contact you might prevent hives appearing.
What can relieve hives? Cooling skin lotions like calamine lotion can relieve itching, as can taking frequent cool baths.
What are the treatments for hives? The main treatment for hives is a course of anti histamine tablets. The prognosis of this treatment is good in many people. Severe ongoing cases can be treated with oral steroids. (21)
Are hives life threatening? Hives are not life threatening but allergic reactions in some people can be. If you are susceptible to anaphylaxis then your doctor can prescribe epinephrine in the form of an epipen that can be carried at all times. It is a self administered measured dose of adrenalin that can treat anaphylactic shock. (22)
Hives are raised, red areas of skin that itch and appear as lumps or weals with defined edges. The main cause of hives is reaction to an allergen but there are also physical causes.
Diagnosis of the cause of hives can be problematic and may on occasions be unknown. Fortunately most cases can be treated, whether or not the cause is identified.
However, whilst this condition can be very uncomfortable and irritating there are steps to relieve the symptoms.