Sarah Beal, 43, from Arley, Warwickshire, has such sensitive skin that the slightest scratch can cause it to swell.But she has also realised that the condition - known as dermatographia - allows her to create patterns and pictures on her skin which disappear within an hour.Dermographism or 'skin writing' is a type of urticaria, or hives - where a raised, itchy rash appears on the skin.Ms Beal said: 'My skin is so sensitive that sometimes even clothes can feel uncomfortable.“When I lie in bed, the quilt can feel like needles pressing into me.'I can scratch my arm or my back and long lines will come up on my arms where I’ve scratched.'But I think being able to draw on my skin is so cool - it’s my party trick.She added: 'The etch a sketch comparison is pretty accurate - although I wish a good shake was enough to get rid of the itching.'Dermatographia is thought to be caused when the cells under the surface of the skin release histamines under the slightest pressure.Histamines are chemicals released in the body as part of an allergic reaction, causing the skin to swell.Ms Bell only discovered her dermatographia just three years ago.She said: 'It just came out of nowhere. At first I just thought my skin was getting more sensitive as I got older.'I’d scratched my skin one day and it got all itchy and raised, but it was nothing serious enough to do anything about.'But as it got worse I knew something wasn’t quite right - I could give my back a scratch and before I knew it my skin would turn red and be really painful.'Eventually I Googled the condition and I just couldn’t believe it.'She also discovered the unusual quirk of her condition just by chance.She said: 'I don’t know why I thought of it, but after seeing my skin raise at the slightest touch, I wondered if I could draw on it.'I grabbed a spoon from my kitchen draw and with the handle I drew a heart on my arm.'When I saw the heart appear on my skin I loved it.'It becomes quite itchy and sore afterwards, but I thought it was so interesting to see it stay on my skin like that.'I quickly took a picture of it and uploaded it to Facebook before it disappeared. I have tattoos so I quite like the idea that you can draw on your skin.'My friends and family think it’s really fun too.'Ms Beal  who runs a cake and confectionery company, takes no regular medication to control her sensitive skin.She said: 'At the moment it’s quite bad, but I just grin and bear it.'When it really flares up, clothes and bedding can be the most painful - it feels like my skin is filled with needles or tiny bits of glass.'Some jewellery can be very painful to wear too, especially around my neck.'I’ve also got two little dogs, and just the tiniest scratch from them can be agony.'But I do like the fact that I can draw on my skin - it’s a little bit quirky and different, a great conversation starter.'Matthew Gass, from the British Association of Dermatologists, said: 'Dermographism or “skin writing” is a type of urticaria.'Swelling is caused by the release of histamine from cells in the skin called mast cells.'In this type of urticaria, itchy weals occur after friction such as rubbing or stroking the skin. This itching may be aggravated by heat.'Weals and red marks also often appear as lines at the sites of scratching, and generally last for less than one hour.'He added: 'Antihistamines block the effect of histamine, and reduce itching and the rash in most people, but may not relieve urticaria completely.'If urticaria occurs frequently, it is best to take antihistamines regularly every day.'There are many different types, including non-sedating and sedating antihistamines, in addition to short acting and long acting types.'The antihistamine tablets can to be taken for as long as the urticaria persists.'(dailymail.co.uk)ANN.Az