Then skin is an extremely important organ which covers the body and provides protection from the world around it. It has a number of mechanisms to protect itself although, when these malfunction, problems such as infection and allergy can manifest themselves. How vulnerable is the skin as an organ?

Before considering whether the organ is vulnerable or not, it is wise to consider exactly what it may be considered vulnerable against. The skin, being the first line of non-specific defence, needs to protect against invasion from foreign microbes, chemicals, physical trauma and even ultra-violet light. To do this, the skin must

a)  Provide an anti-microbial defence. This is the job of the Langerhans cells, that sit in the epidermis (after being produced in red bone marrow).

b)  Maintain the integrity of the epidermis to avoid unwanted exposure to liquid chemicals, sunlight, heat, and many bacteria. It does this through the production of keratin (made by keratinocytes) in the epidermis.

c)   Absorb the ultra-violet light directed at it. This is achieved by melanin (made by melanocytes), also present in the epidermis; the darker the skin tone, the more of this protective pigment is present.

d)  Be able to withstand physical stress. The dermis, the deeper layer of skin, is strong and flexible - this is because it is constructed from collagen and elastic fibres, but is also fortified with fat cells.

Clearly there are several structures in operation that allow the skin to perform its objectives. The skin, whilst a very thin organ in itself, is densely populated with numerous systems of defence, all of which are necessary for optimal function. Because each system interconnects with different biological systems within the body, they can all be vulnerable to different afflictions. All systems must function correctly for the skin, and therefore the body in general, to remain in optimal health, which is perhaps more difficult that it would initially seem when the average human has skin covering over twenty-two square feet.

The skin's vulnerability to problems occurring elsewhere in the body is best demonstrated in the case of increased gut permeability, which itself can be caused by poor diet, antibiotic use or even stress. The increase in foreign bodies entering the blood stream can cause an over-reaction of antibody production by the immune system, and then antibody-mediated inflammation of the dermis upon contact with an antigen. Like so many problems in the body, the route cause of an issue can often be traced to issues elsewhere; through natures intricate design, no organ of the body is invulnerable to disease.

And, like every other organ, the skin is also highly dependent on the vascular system. Without sufficient delivery of vitamins and minerals (eg vitamin A/vitamin C/zinc), the dermis and epidermis will not be able to regenerate itself adequately. In this sense, the skin is as vulnerable as every other organ.

Naturally, there are major differences. The skin has a unique blend of properties to help it stand up to the tests it faces on a daily basis. It is physically strong and yet flexible - it can withstand direct force that may cause haemorrhage in other organs (such as the liver). It also heals very quickly, a trait demonstrated by normal recovery from surgery (eg hernia operations) when the skin appears fully healed when the tissue beneath it is still very inflamed and tender.

It would be very rash to label the skin a vulnerable organ simply because it can be susceptible to disease. In an environment that places regular stress upon the multiple defence systems of the body, it may well be more appropriate to analyse the response of the organ to being compromised.

The skin responds remarkably well to physical wounds and has an excellent capacity to heal itself (provided it receives an adequate supply of nutrients). Depending on the extent of the wound, healing can occur very quickly and consists of a stage of inflammation (where histamine and pro-inflammatory prostaglandins work to attract increased blood supply and, with it, phagocytes and fibroblasts), then proliferation (where granulation tissue develops to restore normal blood supply to the wound) and maturation (where the granulation tissue is replaced by fibrous tissue and collagen is re-arranged).

The skin can also compromised by viruses and bacteria. One example of viral infection is the common human papilloma virus, which facilitates proliferation of the epidermis as above. Impetigo is a bacterial infection, caused by the Staphylococcus aureus, and is often associated with foreign travel. The bacteria cause pustules to develop.

However, the skin can be susceptible to less tangible issues. Whilst allergic reactions within the liver are generally unreported, similar conditions affecting the skin are relatively common, despite the fact that the liver deals with a large number of potentially problematic chemicals. Allergy-mediated conditions of the skin include dermatitis, eczema and psoriasis.

Despite these problems that manifest in discolouration, interruption of skin integrity and often discomfort, this organ often continues to perform many of its functions perfectly well even when it is damaged. This resilience can be seen in action when the skin surface is damaged (eg. a cut as a result of trauma, or stretch marks that appear after tears in the dermis, or even acne vulgaris) it can still perform other functions, such as regulating skin temperature correctly and continuing to fight infection (through specialised immune cells contained within the Langerhans cells in the epidermis).

Likewise, it could be argued that this ability to maintain adequate function masks an inherent vulnerability and sluggish healing. In many situations there are ongoing problems that the skin fails to overcome quickly, such as:

a)      Ringworm, where fungus infects the keratinised area of the epidermis.

b)      Chronic contact dermatitis, whereby inflammation in the epidermis and the outer layers of the dermis is continuous, even after the removal of the offending allergen.

Thankfully, the skin never fails, a vulnerability that unfortunately affects some other vital organs. Like these other vital organs, the skin is massively important - if it was taken away or stopped operating, we would die. But, whilst heart or liver failure are relatively normal reasons attributable for death, skin failure never happens. So there is clearly an inherent durability to the skin as an organ.

To summarise, I would not describe the skin as a vulnerable organ. Obviously it does have its vulnerabilities but these are either an inevitable result of the number of potentially invasive organisms or, as per other organs, or due to poor nutrient delivery from the vascular system. In the main, it is a strong organ that maintains overall function even when compromised, and its reliability in doing such is often taken for granted. It can stand up to both physical trauma and potential infection and does so constantly, thus providing a very strong first line of defence for the body.