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Why Do Hives Develop?
Hives occur when specialized immune cells called mast cells release histamine and other chemicals into the skin.
These substances cause tiny blood vessels to leak fluid into surrounding tissues, producing the familiar swelling, redness, and itching associated with hives.
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While histamine release is a normal part of the body’s immune response, it can sometimes occur even when there is no serious illness.
Common triggers include:
Viral infections
Food allergies
Certain medications
Insect bites or stings
Exposure to heat or cold
Pressure on the skin
Exercise
Emotional stress
In many children, no single trigger is ever identified.
Acute vs. Chronic Urticaria
Doctors generally classify hives into two main categories.
Acute Urticaria
Acute hives last less than six weeks.
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They are often linked to:
Viral illnesses
Allergic reactions
New medications
Foods
Insect stings
Most cases improve on their own or with antihistamine treatment.
Chronic Urticaria
When hives continue for more than six weeks, they are considered chronic.
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Unlike acute cases, chronic urticaria often has no clear cause.
Although persistent hives can be frustrating, many children eventually outgrow the condition with time.
What Is Angioedema?
Some people with hives also develop angioedema, a related condition that causes swelling beneath the surface of the skin.
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Unlike the raised welts seen with hives, angioedema affects deeper layers of tissue and commonly appears on the:
Lips
Eyelids
Face
Hands
Feet
Tongue
Throat
This swelling is often more painful than itchy and may last longer than ordinary hives.
If swelling affects the tongue or throat and causes difficulty breathing, swallowing, or speaking, it is considered a medical emergency and requires immediate medical attention.
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Common Triggers in Children
Finding the exact cause of hives isn’t always possible, but several common triggers have been identified.
Viral Infections
Many children develop hives during or shortly after common viral illnesses such as colds or stomach viruses.
In these cases, the immune response—not the infection itself—often causes the rash.
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Allergic Reactions
Some children develop hives after exposure to allergens, including:
Peanuts
Tree nuts
Eggs
Milk
Shellfish
Certain antibiotics
Bee or wasp stings
Allergic hives usually appear quickly after exposure.
Physical Triggers
Certain environmental factors can also bring on hives, including:
Scratching the skin
Heat
Cold temperatures
Sunlight
Pressure from tight clothing
Exercise
These forms are often referred to as physical urticaria because they result from external physical stimuli rather than allergies.