Understanding skin – Factors that influence skin

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The condition and appearance of our skin is key to our overall health and wellbeing. When skin is in good condition it works hard to protect our bodies from environmental stressors such as irritants, allergens and microbes, regulates temperature and looks and feels smooth, calm, well hydrated and even in colour. There are many factors – both internal and external – that affect skin condition and influence how it looks and feels. For example, because of its compromised skin barrier, hypersensitive skin is more prone to irritation than healthy skin. Some factors we cannot influence, but many we can.  Careful skincare can protect  skin and helps it to look younger for longer.

Internal (endogenous) factors

The internal factors that influence skin include genetics, hormones and specific conditions such as diabetes.


Your genetics determine your skin type.
Genetics also determine the biological ageing of skin.

A person’s genetics determine their skin type (normal, dry, oily or combination) and affect their overall skin condition.

Genetics and biological skin ageing

Genetics also determine the biological ageing of skin which is characterised by:

  • A decline in cell regeneration and renewal.
  • Reduced sebaceous and sweat gland secretions.
  • Degeneration of the connective tissue so that skin is less able to bind in water and loses firmness.
  • Degeneration of elastic fibers which results in reduced skin elasticity.

Biological skin ageing should not be confused with premature skin ageing which is caused by external factors and can be influenced.

Many external factors can influence skin and lead to skin diseases.

A predisposition to skin conditions such as Atopic Dermatitis, Psoriasis and Ichthyosis is also decided by genetics. For example, those born with a genetic Filaggrin (a protein found in skin) deficiency have skin with a weaker barrier function and are prone to sensitive skin and Atopic Dermatitis. With such a predisposition, skin can be triggered more easily by stress and exacerbated by external influences. Therefore it’s important to have a proper skin care routine in place. Read more in dry skin and Atopic Dermatitis.

There are also some diseases – such as diabetes and renal failure – that can impact on skin condition.


Changes in hormones can affect the skin and may cause acne.
Pregnancy can cause hyperpigmentation and affect skin’s moisture balance.

Hormones, and changes in their levels, can have a significant impact on skin:

  • Hormonal changes can trigger the acne of puberty.
  • During pregnancy, hormones can encourage the increased production of melanin and a form of hyperpigmentation known as melasma.
  • Female oestrogen levels decline as part of the biological ageing process and especially after the menopause. Oestrogen has a beneficial effect on the moisture balance of skin and its decline leads to structural changes and the age-related atrophy of skin.

External (exogenous) factors

There are many external factors that influence skin condition. When skin’s natural balance is compromised, it is less able to work as a protective barrier and prone to sensitivity.  The external factors that influence skin health are determined by the environment around us, our overall health and the lifestyle choices we make.

Climate and environment

Sustained exposure to the sun triggers the formation of free radicals, which can weaken skin’s protective mechanisms.

UV Radiation
Free radicals are aggressive molecules responsible for the oxidation process in body tissues that results in cell damage. Healthy skin contains antioxidants that protect it by neutralising the free radicals.

In the epidermis, these free radicals are mainly generated by UV rays. In normal conditions, and with limited exposure to UV, skin’s protective mechanisms are more or less able to cope. If, however, exposure is sustained, skin’s protective mechanisms are weakened and it is less effective as a protective barrier. Under these conditions, skin becomes sensitive and is prone to disease. Years of unprotected sun exposure leads to chronic light-induced damage and, with it, premature skin ageing. UV rays can be particularly harmful to Rosacea-prone skin as its compromised skin barrier can be easily penetrated and the underlying hyper-reactive nerve fibres aggravated.

Read more about the effects of sun exposure and how to protect skin in sun.

Cold weather can cause skin to dry out.
Use warm rather than hot water. Hot water can trigger some skin irritations.

Extreme temperatures, and the speed of change between them, impact on skin skin.

In cold conditions skin reacts by narrowing the blood vessels to protect the body from losing too much heat. Sustained cold temperatures reduce sebaceous gland secretion and cause skin to dry out. Read more in dry skin.

In hot and humid conditions (for example tropical countries or a sauna) sweat glands produce more sweat, leaving the skin moist and shiny and, in some cases, prone to acne.

Some skin conditions, for example Rosacea, can also be triggered by hot temperatures. This is one of the reasons why it is recommended to use warm rather than hot water for facial cleansing, hand washing and bathing.

Chemical influences

Aggressive products
Skin is naturally mildly acidic, with a pH of between 4.7 and 5.75. Aggressive cleansers (such as sodium lauryl sulphate and moisturising products with an alkaline pH) overtax skin’s natural neutralising capability, damage cell structure and impair the barrier function of the outermost layer of the epidermis. As a result, skin can dry out, become hypersensitive and/or is susceptible to skin infections and flare-ups of diseases such as Atopic Dermatitis or Rosacea. Sensitive skin, which is characterised by a weakened protective barrier, is particularly prone to the drying and damaging effects of harsh products.

Aggressive chemicals and skin peelings can damage skin’s pH balance.
Those who work with chemicals need to take special care of their skin.

Certain chemical peels can have a similar affect and it is important to consult a dermatologist to check that a particular procedure is suitable for your skin.

Some people are particularly affected by aggressive products:

  • Small children and the elderly: Young and old skin is less resistant because skin barrier function is either not yet fully developed or is on the decline. Read more in skin in different ages.
  • Those exposed to chemicals in the workplace: Professionals such as hairdressers, masons and industrial workers are in regular contact with detergents, solvents, lacquers and paints, all substances that are harmful to the skin.
  • Those with hypersensitive skin
    Hypersensitive skin is characterised by a compromised skin barrier and hyper-reactive nerve fibres in the epidermis. Aggressive products can damage the skin barrier and trigger the underlying nerve fibres thereby causing unpleasant sensations.

Read more about how to care for body and facial skin and the importance of choosing the right skincare products.

Washing too frequently
Showering or bathing too frequently, for too long and with water that is too hot leads to a loss of skin’s natural moisturising factors (known as NMFs) and surface lipids. Skin dries out and becomes rough. The pH of healthy skin is mildly acidic, and frequent washing with tap water - that ranges from neutral to mildly alkaline - can impact on skin’s natural balance and impair its protective barrier function. Read more about caring for skin on the body and a daily skincare routine for the face.

Certain medications and medical treatments are known to cause dry skin as a side effect.
It is also important to drink plenty of water, especially for elderly people.

A balanced diet will help to keep skin healthy. Research on the best foods for healthy skin is lean, but: 

  • Fruits, vegetables, whole grains and lean proteins (fish instead of meat) are all good for skin. 
  • A diet rich in vitamin C and low in fats and carbohydrates may promote younger looking skin. 
  • Antioxidant-rich foods seem to have protective benefits. These include: yellow and orange fruits and vegetables (e.g. carrots and apricots), blueberries, green leafy vegetables (e.g. spinach), tomatoes, peas, beans and lentils, fish (especially salmon), nuts. 
  • Diets that exclude a particular food group and its nutritional value are not, on the whole, good for skin health. It is, however, advisable to limit the intake of sweets and dairy. It is also important to drink plenty of water, especially for elderly people. 

There is no clear association between diet and the causes of acne.

Therapeutic measures
Certain medicines (e.g. chemotherapy, diuretics, laxatives and the lipid-lowering drugs sometimes taken to treat cardiovascular conditions) and medical procedures (e.g. radiotherapy and dialysis) can make skin more sensitive and prone to dryness.


Healthy lifestyle choices can help to delay the natural ageing process and prevent skin problems:

Managing stress can also promote healthy skin.
A good night’s sleep will give skin cells a chance to repair.

Manage stress
Uncontrolled stress can make skin more sensitive and trigger problems including acne. Stress needs managing: reducing workload, making time for leisure activities and relaxation techniques can help.

Regular exercise has a positive impact on skin health as well as overall fitness. 

A good night’s sleep gives cells a chance to regenerate and helps with skin renewal.

Stop smoking
Tobacco smoke is a major source of skin damaging free radicals. Smoking makes skin look older and contributes to wrinkles by: 

  • Narrowing the tiny blood vessels in the inner layers of skin. This decreases blood flow and depletes skin of oxygen and nutrients such as Vitamin A. 
  • Damaging collagen and elastin: the fibers that give skin its strength and elasticity.

Complete the routine