Tick

• It is the largest and most visible organ in the human body.
• Being the most visible of our organs, the skin also offers us a view into the body tissues that it protects.
• So don’t think of your skin merely aesthetically – think of it as a reflection of your health.

Bullseye

• But while the vast majority of tick bites won’t make you ill, there is one rash that should prompt a visit to your doctor if you spot it.
• Erythema migrans, a rash named for its ability to rapidly expand across the skin, is a hallmark of Lyme disease, a potentially severe bacterial illness.
• This rash forms a classic target pattern, like a bullseye on a dartboard.

Purpura

• Some rashes are given a colourful namesake – purpura is one such example.
• Purpura refers to a rash of small purple or red dots.
• Purpura signals an issue with either the walls of the tiny blood vessels that feed the skin or the blood within them.

Skin spiders

Skin rashes can also take on recognisable shapes. Spider naevi represent an issue within skin arterioles (small arteries which supply the skin with blood). Arterioles open and close to control the loss of heat from the body’s surface. But sometimes they can get stuck open – and a spider-like pattern will appear.

• Crush the body under a fingertip and the whole thing disappears, as your touch temporarily stops the blood flow.
• Treat the underlying cause, and the spiders often vanish with time – though they may persist or reappear later.

Black velvet

• This “black velvet” skin appearance is more commonly seen in darker skins.
• Usually, the condition is associated with disorders of the metabolism – namely type 2 diabetes and polycystic ovary syndrome.

Butterfly rashes

• Cardiac valves have the important role of correctly directing the journey of blood through the heart and preventing backflow.
• The body’s natural response is to preserve core blood volume, shutting off flow towards the skin.
• The net effect can produce a purple-red rash, high across the cheeks and the bridge of the nose, like the outstretched wings of a butterfly.

Dan Baumgardt does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.