Skin rashes can result from a wide range of conditions which often overlap in symptoms and appearance, making it difficult to distinguish the root cause. Eczema is one condition resulting in a skin rash. It is characterised by itchy, chronic and often due to specific triggers. Some key features of eczema stand out from other skin rashes can be differences in duration and causes. Different skin rashes may vary in severity, with some being contagious or dangerous. They may require different treatment methods, so it is important to identify what skin condition is causing a rash.

What is a skin rash?

A rash on the skin can describe any change in skin colour and/or texture which may be accompanied by itching, swelling and pain.

Causes

There are several reasons for a rash. These may include:

Allergies

Rashes caused by allergic reactions are typically bright red rashes with definitive edges, which can appear as clusters of small bumps on the skin.¹ If the allergic reaction is severe, the skin can blister and ooze fluid, similar to a burn. Once the allergen has left the body, the rash will disappear.¹

Irritants

Overuse of certain substances or single use of strong substances irritates the skin resulting in a rash. Irritants are likely to present symptoms of dry, red skin with sensations of burning and painful stinging.

Common irritants include detergents, disinfectants, perfumes and solvents. Once the particular irritant is identified and use is discontinued, the rash typically improves.²

Bites and stings

The resulting rash from a bite or sting occurs from the venom of the organism that has bitten/stung. The appearance of the rash can widely vary depending on the type of insect bite or sting but typically will be red and painful with a swollen bump isolated to one area. Some might cause severe allergic or anaphylactic responses, while other insects can transmit serious diseases through their bites. The bitten area itself usually heals within a few weeks, but the risk of secondary infections can lead to antibiotic treatment.

Viral Infections

Virus infections can cause rashes, which may appear as spots or blisters and are often widespread across the body. Some common viral infections include chickenpox, measles, and shingles.

Viral infections can have a systemic effect on the body, resulting in an array of symptoms, including fever, body aches and fatigue, accompanied by a skin rash.³ Once the infection is treated, the rash along with the other symptoms will begin to dissipate.

Viral infections like chickenpox are highly contagious, and the spread to vulnerable groups can have serious outcomes. Read more on how to protect against viral infections.

Bacterial Infections

Rashes caused by bacteria occur from the skin becoming infected with a type of bacteria, usually from a scratch or cut. This allows the bacteria to enter the body through breaks in the skin barrier. Since there are so many different types of bacteria, rashes will differ in appearance depending on the type of infection a person has. Most will present with inflamed skin, shown by redness and swelling. More severe cases present sores or pus-filled spots that are very painful, such as the case with MRSA, an antibiotic-resistant staph infection that can be life-threatening.

Similarly, viruses and bacterial infections are contagious spreading through skin-to-skin contact or even from contaminated surfaces. Read more on how to protect against bacterial infections.

Skin conditions

Certain skin conditions can also cause rashes to emerge. These may appear intermittently throughout a person's lifetime, sometimes, referred to as “flare-ups.” This occurs in conditions such as eczema, which in some cases can be recurrent and chronic. With eczema, the skin becomes dry, itchy and cracked around folds of the skin like behind the knees or inside the elbows.

Eczema is not contagious, with its origin rooted in multiple complex genetic and environmental factors. It is unlike the other sources of skin rashes that are either transmitted by bacteria, viruses or insects or an autoimmune disease that may cause a skin flare-up like psoriasis.

What is eczema?

Eczema is a common type of dermatitis, which describes any general skin condition that causes inflammation or irritation. Chronic itchiness is a hallmark of the condition, and due to scratching the rash can worsen and become prone to infection. It is most common in children, but can spontaneously occur during any stage of life. Some children will outgrow the condition, and for others, with treatment, symptoms can be effectively managed. 

Symptoms

These include:

• Dry, scaly skin
• Itchiness
• Discolouration/red skin rash
• Thicker patches of skin
• Inflammation/swelling 

Depending on skin type and tone, the rash may appear differently. Lighter skin tends to show red and pink rashes while darker skin has darker purple or brown discolouration.

Causes

Although not fully understood, there is evidence of a genetic component contributing to eczema. Disruptions in the gene that codes for filaggrin protein can contribute to the breakdown of the skin barrier, increasing the likelihood of eczema.⁴

Additionally, an upregulation of protein cytokines has been noted in eczema, contributing to the inflammation and overactive response to environmental stimuli.⁵

Triggers

Eczema triggers will differ from person to person, while some may not have any apparent triggers. Some of the most common ones include:

• Weather conditions - very dry, cold or hot 
• Allergens - dust mites, pollen and food allergies 
• Fragrant items - in soaps, creams, detergents 
• Fabrics - particularly polyester or wool 
• Chemical cleaning products 
• Stress

Types

There are seven different types of eczema, all with similar qualities but may differ slightly in their symptoms, rash presentation and body location. These include:

Atopic dermatitis

The most common type of eczema affects at least 1 in 10 infants in England.⁶ It results in an itchy, dry rash most commonly located in the folds of the skin, notably the neck, arms, legs and face. It is likely caused by defects in the skin barrier, which can be a result of environmental and genetic causes.

Contact dermatitis

It occurs from environmental stimuli. Contact with an allergen results in a subsequent rash in the area the stimuli touched. Similar to atopic dermatitis, the rash is dry, red and itchy.

Dyshidrotic eczema

This type of eczema affects hands and feet, resulting in small itchy blisters. Often a long-term condition that requires treatment. Sometimes referred to as pompholyx.

Neurodermatitis

It presents as a very itchy, scaly skin rash that often doesn’t go away without treatment. After repeated itching the skin thickens and wrinkles and can affect any body part. Another name for this condition is lichen simplex chronicus.

Nummular/discoid eczema

Chronic skin conditions appear as raised circular spots on the skin. It is characteristically itchy and affects the legs and arms but rarely the face or scalp.⁷

Seborrheic dermatitis

A type of eczema that only affects the scalp. It causes scaly skin on the head leading to dry flakes. It is more commonly known as dandruff, and in babies and infants is called cradle cap.

Stasis dermatitis

A different type of eczema is caused by poor circulation in the legs. It causes itchy, dry and thickening areas of skin, often around the ankles where the blood vessels swell. Most often occurs in older patients, as insufficient blood flow increases with age.⁸

Treatment

The treatment course for eczema will depend on the type of illness the individual is suffering from. Treatments can significantly alleviate symptoms of itchiness and dryness to improve quality of life.

Home remedies

• Moisturise often
• Use fragrance-free oils, moisturisers, makeup etc.
• Avoid irritating fabrics
• Try to identify possible food triggers and avoid them
• Coconut oil⁹
• Oatmeal baths¹⁰

Over-the-counter

Some treatments can be bought in local pharmacies or stores. These include:

• Painkillers
• Antihistamines - relieve itchiness
• Hydrocortisone cream - mild steroid medication to reduce inflammation

Prescription

Certain medications need a prescription for stronger treatments. These include:

• Topical corticosteroids - stronger steroid medication to reduce inflammation 
• JAK inhibitors - used to dampen the immune responses that cause inflammation and itching¹¹
• Phototherapy - uses UV light to treat dry and itchy skin, often as a second-line therapy when topical treatments haven’t worked

Key differences between skin rashes 

	Allergies	Irritants	Bites & Stings	Viral Infection	Bacterial Infection	Autoimmune Disease	Eczema
Is it contagious?
Is it localised to one area?
Has the rash blistered or been seeping?
Is the rash associated with flu-like symptoms?
Does the rash have a definitive edge?
Is the rash scaly or dry?
Is the rash chronic?

This is a general guide to the differences between types of skin rashes. It is not a one-size-fits-all rule and exceptions will exist when looking at specific conditions or diseases. Always seek medical advice for correct diagnosis and appropriate treatment.

Summary

Different rashes can display striking similarities to one another, but being able to identify the key differences is essential for accurate diagnosis. It’s important to know which rashes are harmless, and which may require medical attention. While eczema is not severe in most cases, it can be uncomfortable and disrupt everyday life. Getting a rash checked by a medical professional can allow your mind to be at ease, and make sure you receive proper treatment.