A fever indicates an elevated body temperature, typically above 100.4°F (38°C), often signaling an underlying illness or infection. Hives, also known as urticaria, are itchy, raised welts that appear on the skin, varying in size and shape.
The Link Between Fever and Hives
Fever itself does not directly cause hives. Instead, both often manifest as co-occurring symptoms of an underlying condition, such as an infection or an immune system reaction. When the body encounters a pathogen or allergen, it initiates an immune response. This response can lead to the release of inflammatory mediators, including histamine, which contributes to both the elevated body temperature and the development of skin welts.
The hypothalamus, a part of the brain, raises the body’s temperature set point in response to substances called pyrogens released during an immune reaction. Simultaneously, mast cells in the skin can release histamine, causing blood vessels to widen and leak fluid, resulting in the characteristic swelling and itching of hives. While they appear together, they stem from the body’s broader reaction to an internal trigger rather than one causing the other.
Common Underlying Causes
Several conditions can trigger both fever and hives simultaneously. Viral infections are a frequent cause, especially in children, with examples including roseola, measles, chickenpox, common colds, and influenza. Roseola, for instance, often presents with a high fever followed by a rash that may not itch.
Bacterial infections can also lead to both symptoms. Strep throat, caused by Streptococcus bacteria, may result in a fever and a characteristic rash known as scarlet fever. Other bacterial infections like urinary tract infections have also been associated with hives.
Drug reactions are another common trigger for combined fever and hives. An allergic response to certain medications, such as antibiotics like penicillin or nonsteroidal anti-inflammatory drugs (NSAIDs), can cause the immune system to release chemicals that produce both elevated temperature and skin eruptions. These reactions can occur immediately or hours to days after taking the medication. Systemic inflammatory conditions or autoimmune diseases can also present with both fever and hives.
When Professional Medical Help is Needed
Certain symptoms accompanying fever and hives signal a need for immediate medical attention. Signs of a severe allergic reaction, known as anaphylaxis, include difficulty breathing, wheezing, or tightness in the throat. Swelling of the face, lips, tongue, or throat can also indicate a serious reaction that compromises the airway. These symptoms require emergency care as anaphylaxis can rapidly become life-threatening.
Additional indicators for seeking prompt professional help include:
Persistent high fever, especially if it is 103°F (39.4°C) or higher in adults, or specific thresholds for infants and children.
Hives that are painful, blistered, or accompanied by significant swelling beneath the skin (angioedema).
The person appears severely ill, is confused, or experiences a sudden drop in blood pressure.
Hives cover the entire body, are spreading rapidly, or do not improve after a couple of days.
At-Home Relief Measures
For mild cases of fever and hives, several at-home measures can help manage symptoms. Over-the-counter antihistamines, such as diphenhydramine, loratadine, or cetirizine, can help reduce itching and redness by blocking histamine release. Non-drowsy options like loratadine or cetirizine are often preferred for daytime use.
Other relief measures include:
Fever-reducing medications like acetaminophen or ibuprofen to lower body temperature and alleviate discomfort. Follow dosage instructions carefully and avoid giving aspirin to children due to the risk of Reye’s syndrome.
Applying cool compresses to the affected skin or taking a lukewarm bath to soothe itchy skin and help reduce fever.
Wearing loose, comfortable clothing made of breathable fabrics to prevent irritation.
Staying hydrated by drinking plenty of fluids.