Rash! Please help (10 points available!)?

Over the last few days i have noticed i have been getting raised bumps on my skin, it started off as one red bump on the underneath of my left arm, then around 2 weeks later I got a few similar bumps around my groin area and on my arms and chest, these have developed over the last couple of days and have become increasingly sore and raised. I asked my mum about what they are and she had no idea, but she did mention the fact that 2 weeks ago she changed our washing powder brand from Persil non-bio to Daz biological. Please could someone tell me whether these events are linked and possibly what the skin condition might be and how to cure it? Thanks, Will