Introduction

A skin rash is characterised as an area of skin irritation which leads to a change in skin texture, redness, or sensation (such as itching). It can be dry and/or painful and is localised in either one region of the body or covers a large area, which may also result in cracks and blisters.¹ There are numerous reasons why skin rashes occur, including:

• Allergies
• Specific skin conditions, such as dermatitis
• Bacterial, viral, fungal, and parasitic infections (e.g. meningitis or rubella) 
• Side effects from certain medications
• Heat
• Insect bites or reactions to outdoor i.e. hay fever or grass
• Immune system disorders

Despite most rashes being harmless, it is important to recognise and react when a rash requires attention from doctors and other medical professionals to ensure prompt diagnosis. Some rashes may suggest serious underlying conditions as described previously, which require timely intervention to prescribe a suitable treatment. Anyone can get a skin rash, no matter what their age is. Without the help of doctors to detect the root of the problem in rashes using biopsy or skin scraping, these rashes may develop into long-term outcomes such as chronic pain, scarring, spreading of infections, and the progression of worsening symptoms.²

Types of skin rashes

Dermatitis

Commonly known as eczema, dermatitis is an umbrella term for various types of swollen skin rashes. These appear on your hands, feet, face, and behind the knees, and may feel dry, itchy, sore or reddened. Eczema, or atopic dermatitis, is known as the "itch that rashes" due to the rash that appears when you scratch or rub your skin, which is prone to infections. It has been proposed that various factors, including family history, genes, and environmental factors, contribute to the development of dermatitis. The rash may flare up suddenly or develop over a longer time as a more chronic condition.³  

Other dermatitis kinds consist of:

• Allergic contact dermatitis: Is triggered when the immune system of an individual reacts to an allergen, such as metals in jewellery or cosmetic ingredients
• Irritant contact dermatitis: Is triggered when a person frequently touches an irritant, such as soap or detergent
• Seborrhoeic dermatitis: Appears as red scaly patches on the face, scalp and centre of the chest. 
• Dyshidrotic dermatitis (Pompholyx): Appears as tiny blisters on the palms of the hands and soles of the feet

Psoriasis

Psoriasis is a skin disease that causes thick, scaly skin rashes on specific areas, such as the scalp, knees, and elbows, that are sometimes red or discoloured. It affects 2 in 100 people in the UK, which is developed between the ages of 15 to 35 years old. This occurs due to the body’s immune system overacting, which leads to the rapid production of skin cells. As a result, the flaky silvery-white scale tends to cover the rash as an inflammatory response. The exact trigger for the immune system to behave this way is not fully understood; however, scientists speculate that genetics and environmental factors play a heavy role. 

Certain triggers include:

• Obesity
• Smoking
• Dry air or the sun 
• Medications
• Infections⁴

Hives

Hives, also known as urticaria, is a type of itchy skin rash, typically caused by food or medication allergies. The average duration of hives is less than six weeks, while some can persist longer. Some other causes include:

• Disease Infection
• Bites by insects
• Sweating excessively⁵

When to see a doctor?

Most rashes are not life-threatening and usually improve within a few days, although some may take weeks to fully heal. However, some rashes may get infected, worsen, or require immediate medical attention. 

If you notice any of the following symptoms, visit your doctor as soon as possible. 

The sudden appearance and spreads immediately 

The majority of rashes develop in a particular area, such as the arms or legs. When it spreads throughout your body, this type of rash tends to be a result of an allergic reaction or a viral infection. 

Circular-shaped rashes may suggest various disorders including:

• Lyme Disease
• Ringworm
• Sarcoidosis⁶

Blisters and open sores in the rash

A medical professional should be sought for any rash that has begun to blister. Blisters are fluid-filled bumps found under your skin after damage, which are typically filled with blood, pus or clear serum. These should not be popped as it promotes the healing process; however, with skin rashes, blisters frequently burst which can result in an infection and an open sore. 

Seeking medical attention is especially crucial if you have a blistering rash around your eyes, on your genitalia, or in your mouth. Most importantly, do not ignore an infected blister as it could escalate into a skin or blood infection.⁷

Difficulty in breathing and swelling

Immediately seek medical attention if you have any difficulty in breathing or swelling whilst having a rash. This could potentially be an anaphylaxis reaction, which occurs due to an allergy and is life-threatening if no immediate action is taken.⁸

Painful rashes

Itchy, bothersome, and painful rashes might occur. However, a painful rash may indicate the presence of a more serious underlying illness, like genital herpes or shingles. The earlier you start treatment with an antiviral medicine, the more likely it will minimise the intensity and duration of any symptoms caused by the virus. If these illnesses are not treated, it can lead to persistent problems that may develop into a long-lasting condition and severe pain.⁹

Accompanied by a fever

If you have a fever of 37.7℃ or more and a rash together, the body may have a viral infection. 

Some disorders that affect the immunity of a person and have symptoms of fever and rash together include:

• Measles
• Glandular fever
• Scarlet fever
• Shingles¹⁰

Infected rash

The rash might result from an underlying viral infection. However, if you can't help but scratch, the rash site may become infected with bacteria. 

Symptoms of an infected rash that requires immediate A&E attention consist of:

• Crusting
• Red lines close to the rash
• Swelling 
• Warmth to the area
• Green or yellow fluid or pus coming out from the wound¹¹

Summary

Rashes are patches of irritated skin that result in a change to the skin texture, redness, or sensation. These can be unpleasant and may appear lumpy, enlarged or bumpy. A rash may occur due to several factors, such as allergies, infections, insect stings, or immune system illnesses. Although most skin rashes can be treated at home and eventually fade, painful rashes, that appear to be infected, or have spread quickly to other areas require healthcare consultation. Dial 999 if you have other symptoms on top of the rash and seek medical attention at once.