Is there any history of trauma or injury at the sites? You could be suffering from a condition called Dermographism.
'Patients with simple dermographism are asymptomatic and require no therapy. Recognition of the problem, avoidance of precipitating physical stimuli, reduction of stress and anxiety are important factors in medical care. Also, scratching because of dry skin can be reduced with good skin care and emollients. H1 antihistamines are the drugs of choice.'
You could read about the condition at the following links -
In this condition, the skin reacts to rubbing by an object by developing swelling, inflammation and redness.
Since it is an urticarial rash, it may be caused by nearly all substances in our environment. However, you may try and get some relief by use of anti-allergics and ice packs. This usually helps and subsides the reaction in many cases.
You should read this and let us know if you need any further information.
Hey thanks a lot for the reply, It does actually look like I have dermatographic urticaria. I can write on my skin and a red mark will stay there for up to an hour.
Although, all the pictures I've looked at other cases of Dermatographic Urticaria look nothing really like the mark on my arm.
There is no history or injury at the site (my arm).
Thank you once again.. I might actually get this checked out at a doctor if it persists to get some anti-allergics as you said.