Our face spiders - friends or foes?

You may be surprised (or perhaps horrified) to know that you have spiders on your face right now. In addition to the millions of bacteria, viruses and fungi that make up our skin microbiome (the community of microorganisms on our skin) we have microscopic eight-legged creatures that also make a home in our skin. In humans there are two species; Demodex folliculorum which reside in our hair follicles and Demodex brevis which are found in our sebaceous glands^[1]. They are just two of the 46,000 different species of mites that form the Arachnid family along with spiders and ticks.

Thankfully, the arachnids on your face aren't as big as this Christmas Lights Jumping Spider! Jumping spiders sometimes follow convoluted routes when hunting, even losing sight of their prey. How and why they do this, especially given the size of their brains, is also an open question. Image credit: public domain, via USGS (Flickr)

While studies suggest that we aren’t born with these creatures on our skin, but acquire them over time as a result of skin to skin contact with our mothers, how the spiders get onto us remains a fundamental mystery. Their numbers increase as we get older, but we don’t know why this is^[2,3]. To date scientists have been unable to culture Demodex long term outside the body, as they dry out very easily^[4,5]. As a result they are difficult to research and little is known about their life cycle apart from the observations of Spickett in 1961. He suggested that the mites roam the surface of our skin at night in order to breed. Females lay eggs within our hair follicles where they hatch and develop into adults and the cycle starts again^[6].

Autoimmune diseases - the friendly fire of our immune system

Autoimmune diseases affect millions of people, and have become an important focus of scientific research in the past decade due to their apparent increase in prevalence worldwide^[1][2] - and yet little is known about their cause. Our body’s immune system is a pathogen-fighting machine, finely adapted to seek and destroy any foreign invaders which might cause damage within our bodies. To do this, it needs to be able to work out what is dangerous foreign material and what isn't, and sometimes it can get confused. Common allergies like hay fever occur when the body treats harmless pollen like a dangerous pathogen, and mounts an immune response. This can be irritating, but the real problem comes when your immune system becomes convinced your own body is a danger, and begins attacking itself. This is what happens in autoimmune diseases

The precise cause of these diseases is unknown but is thought to be a combination of both genetic and environmental factors^[3]. It is known that relatives of people with autoimmune diseases are more likely to develop them, yet multiple studies have shown that in a pair of identical twins, with identical sets of genes^[4], sometimes only one twin will develop an autoimmune disease.

This suggests that while genetic factors can predispose you to an illness, an environmental factor may be involved in triggering the development of the disease. One type of environmental factor associated with autoimmunity is infection. Exposure to numerous common viruses has been described as a risk factor for developing autoimmunity. A well-known example is the Epstein-Barr virus (EBV) which is the cause of glandular fever (also known as the ‘kissing disease’ or Infectious Mononucleosis). Over 90% of the adult population are latently infected with EBV, meaning the virus is present in their system but does not cause any symptoms.

All viruses have the ability to evade the host’s immune system in some way - this ability to hide from the immune system enables viruses to survive. Immune suppressive responses have evolved in viruses over time, and they have even stolen bits of our immune system that are beneficial to them. Image credit: By Liza Gross^[8] ©2005 Public Library of Science (CC-BY).

Just like any other virus, the EBV virus is able to evade its host’s immune system. One way it does this is to produce proteins which modulate the host’s immune system. In the majority of people this has no detrimental effect; however in people with genetic susceptibility to autoimmunity an immune response to the body's own tissues is initiated. We have not yet been able to explain why it affects this small proportion of people, but not the many others also infected.

Why do we sleep? [SCIENCE VIDEO]

We spend a third of our lives doing it, yet it still isn't clear why we need to sleep. In fact, there’s so many things we don’t know about sleep, that we don’t have time to talk about them all today.

This is the first of our articles to be made available as an animated video. 
An audio version of this article is also available!

What we do know is that we can’t function without it. After missing just one night’s sleep, you are likely to find yourself feeling hungry, emotional and unable to concentrate. Decisions will become difficult to make, your reactions will slow, you may become forgetful, and your vision can even be affected. Going without enough sleep can weaken the immune system, making you susceptible to colds and other infections, and can even increase your blood pressure.

So it is clear that sleep is vital, but why? Scientists just can’t agree…