What are the other Names for this Condition? (Also known as/Synonyms)

• Prickly Heat

What is Miliaria Rubra? (Definition/Background Information)

• Heat rash is an itchy and slightly uncomfortable rash that occurs typically during hot-humid weather, due to excessive sweating. It is a commonly observed condition in children and adults
• There are three main forms of heat rash (or miliaria), which are termed miliaria crystallina, Miliaria Rubra, and miliaria profunda. Miliaria Rubra is the most common form of heat rash. It is also known as Prickly Heat
• In Miliaria Rubra, the deeper layers of the skin lining (epidermis) are involved causing leakage of sweat and associated inflammation resulting in the formation of red papules. The condition usually develops from blocked sweat glands caused by several factors such as tight clothing and intense physical activity
• The signs and symptoms of Miliaria Rubra include the presence of numerous itchy red bumps, commonly seen in the trunk and neck region. The condition may also be accompanied by heat intolerance and fatigue
• Miliaria Rubra is generally not a serious condition. It usually goes away without the need for any treatments. In a vast majority of cases, the prognosis is excellent

Who gets Miliaria Rubra? (Age and Sex Distribution)

• Miliaria Rubra can affect individuals of all ages, but is more common in adults
• There is no gender preference noted and both males and females are affected
• The condition is seen worldwide across all races and ethnic groups

What are the Risk Factors for Miliaria Rubra? (Predisposing Factors)

Miliaria Rubra is a form of heat rash. In general, the risk factors for heat rash may include:

• Continuously lying on one side of the body for a prolonged period, such as observed in those who are bedridden
• Athletes who undertake intense physical activity
• Residing in or traveling to hot and humid climates; living in tropical regions
• Working outdoors in hot and humid conditions, such as farmhands, construction workers, etc.
• People who work in hot-humid (indoor) environments such as mine shafts or certain industries
• Presence of high levels of the bacterium Staphylococcus epidermidis increases one’s risk. S. epidermidis is a bacterium that safely lives on the surface of the skin
• Underdeveloped sweat ducts
• Wearing non-porous synthetic clothing, especially during hot periods
• Frequent skin infections
• Cancer treatments such as radiotherapy
• It may occur as a side effect of certain medications and may include:
  • Induction chemotherapy
  • Drug-induced hyperhidrosis, or the excessive sweating occurring from using certain medications
  • Stevens-Johnson syndrome
  • Toxic epidermal necrolysis
• Genetic disorders such as Morvan syndrome and pseudohypoaldosteronism type I

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Miliaria Rubra? (Etiology)

• Miliaria Rubra is the most common form of heat rash. Blocked pores that trap sweat under the skin cause heat rash
• Visible signs of inflammation emerge when the trapped sweat leaks into surrounding skin and forms tiny pockets

The sweat glands may be blocked due to many factors including:

• Tight restrictive clothing
• Intense physical activity
• Presence of a high amount of the bacterium Staphylococcus epidermidis that produces a sticky substance

It is important to note that heat rash is not an infectious condition, and it cannot be transmitted from one individual to another.

What are the Signs and Symptoms of Miliaria Rubra?

The signs and symptoms of Miliaria Rubra depend on the severity of the condition. Miliaria Rubra occurs in the outer layer of skin (epidermis) and is characterized by:

• Red bumps or blisters that are 2-4 mm in size
• Itchy or prickly feeling
• Generally, the neck and shoulder region is affected
  • In children, the trunk, neck, armpits, and groin are usually involved
  • In adults, the upper trunk, scalp, neck, and flexural folds are commonly involved
• There is little sweating around the affected area
• Intolerance to heat
• Fatigue

Adults with heat rash may present fever.

How is Miliaria Rubra Diagnosed?

Miliaria Rubra may be easily diagnosed and does not have the requirement for detailed tests and/or invasive exams. A healthcare provider or dermatologist will be able to visibly determine the presence of the condition.

Nevertheless, the following tests and exams may be undertaken, if necessary:

• A complete physical examination and a thorough medical history
• Dermoscopy: Dermoscopy is a diagnostic tool where a dermatologist examines the skin using a special magnified lens
• Skin or tissue biopsy: A skin or tissue biopsy is performed and sent to a laboratory for a pathological examination, who examines the biopsy under a microscope. After putting together clinical findings, special studies on tissues (if needed) and with microscope findings, the pathologist arrives at a definitive diagnosis
• Cultures of skin biopsies, if necessary
• Blister smears may be undertaken to rule out herpes simplex infection

Note: A skin/tissue biopsy is normally not necessary to diagnose heat rash but may be performed to rule out other causes or similar conditions/infections.

A variety of conditions may exhibit similar signs and symptoms. Hence, a differential diagnosis to eliminate other conditions or infections may be considered, before arriving at a definitive diagnosis.

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Miliaria Rubra?

Miliaria Rubra will usually clear by itself without any complications. In some rare cases, the potential complications may include:

• Increased sweating (hyperhidrosis) may occur in non-affected body areas
• Secondary bacterial infection of the rash, usually by Staph bacteria
• Heat exhaustion

How is Miliaria Rubra Treated?

The goal of treatment for Miliaria Rubra is to cool the body and reduce sweating. Once the body has sufficiently cooled, the skin condition is known to disappear. 

Cooling the body may be achieved by:

• Sitting next to a fan or air conditioner/cooler
• Bathing in cold water
• Stopping any physical activity
• Cold water compresses

Topical creams that may be used for severe cases include:

• Hydrocortisone, a weak steroid, to reduce inflammation
• Anhydrous lanolin, to reduce pore blockage
• Calamine lotion, to reduce itching
• Antibiotics may be prescribed for secondary infections, if any

Over-the-counter ointments (not prescribed by healthcare providers) should be avoided as they may cause blockage of the pores and worsen the condition.

How can Miliaria Rubra be Prevented?

Certain preventive measures for Miliaria Rubra include:

• Regularly changing positions of individuals who are confined to a bed or chair
• Sleeping in a well ventilated area
• Using unscented soaps and detergents
• Wearing light, loose fitting cotton fabrics in humid weather
• Avoiding creams or makeup that block pores
• Treating skin infections promptly and adequately
• Review treatments using medications that cause heat rash

What is the Prognosis of Miliaria Rubra? (Outcomes/Resolutions)

• In a vast majority of cases, Miliaria Rubra has an excellent prognosis, as it goes away on its own
• Severe cases may need appropriate treatments using topical applications

Additional and Relevant Useful Information for Miliaria Rubra:

Cleaning the skin too hard with strong chemicals or soaps may aggravate the skin condition. Care must be taken avoid strong soaps and chemicals that can potentially worsen the condition.