Hong Kong’s Climate is the Culprit of Eczema in Children

Eczema is a common chronic disease in Hong Kong. It is estimated that approximately 30% of children in Hong Kong suffer from eczema.[1] The severity of eczema varies with each individual and their source of allergens can be quite diverse. Hong Kong’s climate is one of the most common causes of eczema. This article will focus on how the climate in Hong Kong can cause eczema triggers and useful ways to prevent weather-induced eczema.  

The Climate of Hong Kong

Hong Kong is located on the southern coast of China. It is a small city that is densely populated and packed with a lot of high rise buildings. There is a long coastline and isolating islands which gives Hong Kong its unique climate. 

Hong Kong has a subtropical climate with hot and humid summers with frequent precipitation. It is not surprising to see wet floors and walls with dripping water lines during the summer season. 

According to the Hong Kong Observatory, temperatures in May to August typically exceed 31°C and have a high relative humidity of over 80% which makes the body feel hotter than stated. Also, it rains four days a week. [2] The hot and humid weather in Hong Kong often leads to eczema. 

How does Hong Kong’s Climate trigger eczema?

Firstly, the hot weather in Hong Kong is closely related to the occurrence of eczema. The high environmental temperature can enhance vasodilation, increasing blood flow to the skin which makes the skin surface hotter.

The hot skin will then stimulate sweat glands to produce sweat. As sweat is low in pH, it can irritate the skin which then enhances the Th2 and Th17-mediated inflammation. This may cause skin peeling.  [3]

Filaggrin is a protein that is important for the formation and hydration of the dead skin layer. It helps the skin to stay smooth and moisturized. Approximately 50% of eczema patients have filaggrin mutation, which caused the outermost skin layer to be flaky and dry [4]. The skin is then more prone to infection to foreign allergens such as sweat which causes skin irritation.[5]

Moreover, frequent rainfall in Hong Kong can also be a factor leading to eczema in children. Although high relative humidity can help retain moisture on the skin and reduce eczema irritations, excess moisture e.g., heavy rainfalls can trigger eczema by bringing allergens to the skin through rain.[6]

The heavy rainfall increases the relative humidity of Hong Kong and makes the environment wet. This can enhance the growth of allergens such as molds and dust mites which can directly cause eczema flare ups in children. [6]

When it is raining cats and dogs, parents tend to bring their child indoors. Shopping malls often have strong air conditionings which increases the evaporation of moisture on the skin. The removal of moisture will make the skin dryer. 

The triggering of eczema doubles in rainy days as there is a frequent climate changing between outdoor and indoor areas. The rainy outdoor environment can trigger eczema by promoting growth of allergens such as molds. The dry atmosphere indoors can enhance moisture removal which causes the skin to be dryer.

The typical summer climate in Hong Kong increases the severity of eczema. During summer, the wind flow is quite low and the temperature is high, this leads to more sweat produced and trapped on the skin surface as the rate of evaporation is low. [6]

As more sweat is present on the skin surface, more allergens can be present on the skin surface as sweat is sticky. Some common allergens trapped are dust and mites. This hence causes an increased chance of skin flare ups and itching.  

Together with industrialisation and poor ventilation in Hong Kong, it increases the amount of dust trapped in the environment which hence increases the possibility of eczema conditions when the patient is allergic to dust. 

Tips to Reduce Eczema in Summer

As an individual with eczema, I always tried to come up with ideas to combat my weather- induced eczema.  Here are some suggestions that have worked well for me and possibly for you too!

1. Avoid putting a thick layer of cream on the skin before going out. 

Many parents understand the importance of skin moisturization to prevent cracked skin and triggering of allergens. However, adverse effects can occur if one puts too much cream. 

As cream is quite sticky, this will increase the chance of dust or allergens sticking onto your skin surface and causing eczema triggers. When the body absorbs the cream, the allergens will eventually touch the skin and cause flare ups. 

There are two ways to improve this situation. Firstly, choose a cream that is watery and thin in texture as this allows your body to absorb the cream faster which hence reduces the allergens attached. It is also beneficial to put thinner layers of cream multiple times instead of a thick layer of cream daily. 

Moreover, the time of putting cream is crucial for treating eczema. As the body needs time to absorb the cream after applying it, it is best to put cream before sleep and after taking a shower. This enhances the cream absorbance and moisturizes your child’s skin better which hence reduces the occurrence of eczema.

2. Use a small electric fan when going out during the summer.

During hot and wet summers, it is always handy to bring a small electric fan for your child.  The electric fan can increase the airflow and reduce the water trapped on your child’s skin. This hence reduces the allergens trapped as well. 

The fan can also cool down the skin temperature of your child, this is effective in reducing his/her body temperature and reducing the sweat produced. It can also reduce the potentiation of skin inflammation.

3. Use a wet towel to wipe off the sweat

It may be impossible to completely prevent sweat production during hot summer days. So, bringing a wet towel to wipe off the sweat can effectively reduce the triggering of eczema and cool down the surface of the skin. [7] Sweat is always generated when your child runs around in the park or plays in the sand.  You can always wrap a damp towel around him/her neck to prevent the sweat from staying on the skin. The towel can absorb the sweat produced from the head and the neck which are two common areas where sweat is produced. 

You can also use a wet towel to help your child wipe his/her body from time to time during outdoor activities in summer. This can help to reduce the sweat-induced allergy reactions and hence lower the chance of skin flare ups and inflammations. 

In conclusion, the hot and humid summer in Hong Kong can lead to an increase in the flare ups in children. Sweat produced and environmental allergens can cause skin irritations and itching. Some ways of climate-induced eczema is to wipe off sweat with a wet towel, apply a thin layer of cream and use an electric fan to cool down the skin. 

​​References  

1. Cheng, N.S., et al., Measuring the quality of life of the families of children with eczema in Hong Kong.Asia Pac Allergy, 2019. 9(3).
2. Observatory, H.K. Climate of Hong Kong. 2021  [cited 2022 10 Jun]; Available from: https://www.hko.gov.hk/en/cis/climahk.htm.
3. Sargen, M.R., O. Hoffstad, and D.J. Margolis, Warm, humid, and high sun exposure climates are associated with poorly controlled eczema: PEER (Pediatric Eczema Elective Registry) cohort, 2004-2012. The Journal of investigative dermatology, 2014. 134(1): p. 51-57.
4. McGrath, J., Skin barrier genetics: filaggrin and the dermatologist. Hong Kong J. Dermatol. Venereol, 2011. 19: p. 116-122.  
5. McLean, W.H.I., The allergy gene: how a mutation in a skin protein revealed a link between eczema and asthma. F1000 medicine reports, 2011. 3: p. 2-2.
6. Silverberg, J.I., J. Hanifin, and E.L. Simpson, Climatic Factors Are Associated with Childhood Eczema Prevalence in the United States. Journal of Investigative Dermatology, 2013. 133(7): p. 1752-1759.
7. Leung, T., et al., Management of atopic dermatitis in children: 2020 review by the guidelines development panel of Hong Kong College of Paediatricians. Hong Kong Journal of Paediatrics, 2021. 26(1): p. 42-57.