The impact of climate change on skin
What is climate change?
Climate change is a lasting alteration in patterns of weather caused by factors such as oceanic circulation, variations in solar radiation, plate tectonics, volcanic eruptions, and human factors. These may impact global or local temperature, humidity, rainfall, and weather extremes.
Colloquial use of the term “climate change” specifically refers to environmental changes caused by human factors, including global warming due to the production of gases that may trap heat in the atmosphere — carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and fluorinated gases.
Climate change has been called a “risk-multiplier” rather than a risk-generator or risk factor, due to it worsening pre-existing climate-related health concerns.
Climate influences a wide range of systemic diseases and conditions. Heat exposure, a combination of air temperature, humidity, air movement and heat radiation, can present an environmental hazard. The most common measures used to describe heat stress are the wet bulb globe temperature (WBGT), and universal thermal climate index (UTCI). A WBGT of 29 degrees has been shown to reduce work performance and to cause a wide variety of respiratory, cardiac and gastrointestinal diseases.
As skin is exposed to the environment, it is especially vulnerable to increased heat and humidity. In this article, we describe the effects of a warmer environment on cutaneous infections and inflammatory diseases of the skin.
Who are most vulnerable to the impact of a hotter environment?
- Infants and children
- Older people
- Pregnant women
- Outdoor workers and athletes
- Indoor workers in an environment without cooling
- Tourists or those unfamiliar with specific local heat risks
- People with chronic medical conditions such as renal disease and alcohol dependence
- People with diseases that impair awareness, mobility and behaviour (such as Parkinson disease, dementia, developmental delay).
- Families and nations under financial stress and unable to adjust their environment
- People living in urban areas, because cities absorb, generate and retain more heat than rural areas
- People living in homes not designed to reduce heat stress
- The socially disadvantaged (suffering from low economic status, homelessness or social isolation)
Cutaneous infection associated with warmer climate
Warmer conditions lead to a greater prevalence of cutaneous infections, including:
- Bacterial infections such as impetigo, cellulitis and boils
- Fungal infections such as pityriasis versicolor and tinea pedis
- Viral skin conditions.
One study showed that for every 1°C rise in average temperature, the rate of hand foot and mouth disease increased by 10% and for every 1% increase in relative humidity (under 65%) the rate increased by 6.6%.
Vector borne disease
Mosquitoes, ticks, and fleas are vectors that carry pathogenic viruses, bacteria, and protozoa, which can be transferred from one host (for example a mosquito) to another (for example a person or animal). Temperature plays an important role in the spread of vectors and vector borne disease. Warmer conditions lead to faster replication of certain viruses and vectors and increased rates of transmission.
- Lyme disease (Borrelia burgdorferi)
- Spotted fever rickettsia
- Powassan virus
- West Nile virus
- Zika virus
- California serogroup viruses
- Eastern equine encephalitis
- St. Louis encephalitis
Heavy rainfall and flooding often leads to outbreaks of waterborne disease, which are predicted to increase with climate change. Water sources may undergo increased contamination from flooding or become stagnant from drought. Flooding causes disease to spread as people move en masse to seek dry ground.
Climate factors have been identified as important in outbreaks of the following waterborne diseases:
- Bacterial infections: Escherichia coli, campylobacter, leptospirosis, typhoid fever and vibrio species
- Parasites: toxoplasma and cryptosporidium
- Viruses: hepatitis A and E, norovirus and polio
- Helminth infestation: schistosomiasis.
Flooding and droughts may lead to lack of fresh water for washing and cooking, especially in resource-poor nations. Warmer waters can cause outbreaks of shellfish-borne disease, such as Vibrio parahaemolyticus.
Increases in temperature and humidity cause food to decay and thus increased consumption of mycotoxins, which are metabolites of moulds. Mycotoxins may also cause disease by penetrating through the skin.
- About 4.5 billion persons living in developing countries are chronically exposed to largely uncontrolled amounts of aflatoxin from aspergillus species (found in corn, peanuts and decaying vegetation).
- Aflatoxin can cause liver disease, growth restriction in children and animals, cancer and immunosuppression leading to vaccination failure and decreased resistance to infectious disease.
- Other mycotoxins have been associated with skin irritation and rashes.
Phycotoxins are potent natural toxins produced by some marine algae and cyanobacteria species. Outbreaks or algal blooms are often colloquially known as as “red tides” or “green tides”. Seafood intended for human consumption can be contaminated in massive quantities.
- Adverse health effects associated to phycotoxins and HABs can occur through oral, respiratory or dermal exposure.
- Human intoxications are often misdiagnosed and therefore not reported to public health authorities.
- Several phycotoxins are neurotoxic, potentially lethal, and associated with chronic morbidity.
- Some cyanobacteria species produce phycotoxins that are dermatotoxins. These include;
- Aplysiatoxins — which cause respiratory symptoms and skin irritation
- Lyngbyatoxin — which case smooth muscle contraction and skin irritation.
Warmer climate and hot surfaces, bushfires and building fires may lead to thermal burns.
Exposure to ultraviolet radiation
Measured levels of ultraviolet radiation are mainly independent of heat and humidity. However, higher outdoor temperatures in previously temperate climates might result in people wearing less clothing and spending longer periods outdoors, and thus increase exposure of the skin to ultraviolet (UV) radiation.
UV damage includes:
Inflammatory skin diseases
- Contact dermatitis is more common and more severe when ambient temperature is higher
- Asteatotic eczema is less common in hot, humid climates compared to dry, cool climates.
- Prevalence of atopic dermatitis may be affected by changes in aeroallergens such as the dust mite, Dermatophagoides pteronyssinus.
- Higher temperatures cause more intertrigo, especially when associated with obesity and diabetes.
- Hyperhidrosis leads to miliaria and transient acantholytic dermatosis (Grover disease)
- A hot environment may also cause flares of rosacea, cholinergic urticaria, and heat urticaria.
Inflammatory skin diseases aggravated by hot conditions
Barriers to long term projections about interaction of climate factors and disease
Better early warning systems and prediction tools would enable prevention and management of disease epidemics — including those affecting the skin.
Barriers to making long term epidemiological assessments and projections include:
- Paucity of disease data
- Changing health systems, socioeconomic status and land use
- Prolonged timescale – it is difficult to assess changes in climate without data of consistent quality over decades and centuries of weather events
- Diagnostic inaccuracy and changing disease case definitions
- Poverty – the countries which support the poorest and most vulnerable populations are likely to suffer most from climate change.