Key learning points:
– Miliaria ruba is the medical term for heat rash (or prickly heat) and is a skin condition caused by blockage of the eccrine sweat duct
– There are no medical treatments; only preventive measures to counteract overheating, sweating and friction
Nurses and health visitors have an important role in supporting parents to manage heat rash in infants
Heat rash or ‘prickly heat’ is a lay term for a dermatological condition miliaria rubra, which is characterised by the occlusion of eccrine sweat ducts, resulting in the retention of sweat within the skin.1 This article will describe signs and symptoms of miliaria rubra, treatment options and practical parental advice.
Miliaria rubra is a subtype of miliaria, the other subtypes are miliaria crystalline and the more severe, miliaria profunda. The classification is according to the level of eccrine sweat duct blockage and it is important to discuss all three subtypes to give a broader understanding of this common skin condition, although the more severe forms would not be seen in infants.
Miliaria crystalline is the most common type seen in infants, with a reported prevalence rate of 4.5% of babies with a peak frequency at one week of age.2 It is generally seen in infants who sweat profusely due to febrile illness and occurs because the sweat ducts have not developed patency.3 This form of miliaria appears as transient clear vesicles, which rupture and resolve without symptoms or complications.3
Miliaria rubra (subtype of miliaria referred to as heat rash or prickly heat) is the common symptomatic form. It can affect all ages, especially infants. It is more common in tropical climates, but can occur during the summer months in the UK or when families travel to the Mediterranean or tropical climates. Heat rash can also occur due to overheating, including lying on waterproof bedding. It can also arise in areas of the body that are prone to friction, especially body flexures (folds), neck and limbs.3
Miliaria profunda is the most severe subtype, caused by total blockage of the eccrine ducts at dermal level. It can become a chronic disease and is a complication of milaria rubra, because it always follows repeated attacks.4 Miliaria profunda usually affects people who live in tropical areas, and not temperate climates.3
Signs and symptoms
Miliaria rubra is seen throughout infancy, more frequently in the neonatal period.5 It appears as crops of red lesions, which are often symmetrical and more likely to be situated in the flexural areas, especially neck, groin and axillae. It can also be seen on the face, scalp and upper trunk. Lesions are also most likely to occur at body sites that are occluded or have been in contact with plastic or polythene, such as waterproof pants or mattress covers.5 Crops of lesions generally subside within a few days, but are likely to recur. When miliaria is an extensive eruption, the infant can become distressed and restless.5
Miliaria rubra appears to be caused by eccrine sweat duct obstruction deep in the dermis because the neonate’s thermoregulatory system is immature.5 It is believed that infant microflora also plays a part, as the production of miliaria is believed to be an increase in certain normal staphylococcus epidermidis bacteria, which lives on the skin. These produce a sticky substance, which blocks the sweat ducts. Leakage of sweat through the walls of the duct behind the block is responsible for production of the miliaria spots and for further irritation of the skin.6
Environmental factors also play a part, as infants are often subjected to warm and humid conditions – in home environments and if they are taken to a different climate.5
Miliaria rubra can cause heat exhaustion and, in profuse eruptions, secondary infection, due to skin irritation and damage to the epidermal barrier caused by scratching.3
Treatment options for miliaria rubra
There are no medical treatments for milaria rubra. Primarily, treatment is to avoid sweating and friction in body flexures and prevention of overheating.3 The infant should be kept as cool as possible. Fans or air conditioning are helpful, although air conditioning can also have a drying effect. Moisturising with bland medical emollients is advised for infants with miliaria rubra to reduce irritation and help prevent skin damage from scratching.
The classic itch treatment calamine lotion is not advised, as it is a suspended powder formulation and therefore has a drying effect on the skin.3 If secondary infection occurs, topical or systemic antibiotics are indicated.3 The evidence for antibacterial preparations for miliaria rubra is disappointing but preparations may have a role to play in prophylaxis.3
Parental advice for coping with heat rash
Nurses and health visitors have an important supportive role.
Preventing overheating is key, as the only effective treatment is avoidance of sweating.3 Skin irritation due to friction needs to be avoided; so clothing should be breathable. Natural fibres are recommended. Plastic under-sheeting and plastic overpants should be avoided, especially in hot weather. Parents should
also be advised to avoid skin irritants, which includes washing with soap.5
Emollients can help to provide skin comfort and help prevent itching. Greasy or heavy emollients, which are ointment based, should be avoided, as they could cause further irritation by blocking the sweat ducts. A cream or lotion would be suitable; and can additionally be kept in the fridge. An emollient containing an antimicrobial may be a good choice to help reduce the increase in staphylococcus epidermidis bacteria.5
Parents travelling with infants to the tropics or hot and humid climates should be advised to keep an infant very cool with loose layers of natural-fibre clothing, such as cotton or silk. It is also very important to keep the infant well hydrated. If the infant is overheating, they can be moved into air conditioning. Even doing this for short periods of time is known to help. Infants can be given tepid baths or cold compresses, but not for more than 20 minutes, as this may reduce core body temperature too much.6
As miliaria rubra occurs in summer or hot climates, parents will ask for advice on sun protection. Some sunscreens may be irritant, so advice from the National Eczema Society on sunscreens can be followed.7 Mineral-based sunscreens (containing titanium dioxide) that block out the sun are generally less irritant than chemical absorbers.7 A lighter lotion or spray would also be a good choice, as thicker formulations may block the sweat ducts.
Miliaria rubra is common in all infants, and is caused by developmental and environmental factors. It can be prevented and predicted in hot and humid weather, at home or abroad. Therefore all nurses and health visitors should be aware of how to prevent and treat it, and provide practical and evidence-based advice to parents.
1. Feldman SR, Sangueza OP, Pichardo-Geisinger R. Dermatopathology Primer of Inflammatory Diseases 2014;1:27.
2. Hidano A, Purwoko R, Jutsukawa K. Statistical survey of skin changes in Japanese neonates. Paediatric Dermatology
3. Coulson IH. Disorders of the sweat glands. Rook’s Textbook of Dermatology 2010;14:15-16.
4. Qi He, Leow M, Chong WS. Care of patients with miliaria profunda: patient education and management. Dermatological Nursing 2015;14:(1) 32-34.
5. Paige D. Skin Disorders in the neonate. Rook’s Textbook of Dermatology 2010;17:7
6. DermNetNZ. Miliaria. DermNet NZ. 2015. dermnetnz.org/hair-nails-sweat/miliaria.html (accessed 12 June 2015).
7. NHS Choices. Prickly heat. NHS Choices, 2015. nhs.uk/Conditions/prickly-heat/Pages/Introduction.aspx
(accessed 12 June 2015).
8. National Eczema Society. Eczema and the sun. NES, 2014.
eczema.org/factsheets (accessed 12 June 2015).