hello, I would like to let you know that the blood we donate is not dirty. It is given to the patients who are in serious need of blood transfusion.The reason for your pimples is not solely related to impure blood. Donating blood doesn t mean that you ste giving away dirty blood. The blood is taken from one of the vein which carries deoxygenated blood.So the blood is not dirty it is deoxygenated. Before donating blood there are many things that are checked,for good of the person who is receiving the blood and also the one who is donating the blood. So you won t be able to donate blood just like that. You should be having the ideal conditions to donate the blood. Which you will understand when you plan to donate the blood and you will be examined for it. I would suggest you to consult a dermatologist for the problems regarding pimples. And you can try basic things like keeping the skin clean all the time. Avoiding the things that bring trouble to your skin. Drinking adequate water and staying away from foods that are very oily.Not using harsh chemical products on skin as it is very sensitive to these. A dermatologist can give you better advise after examining the type of skin you got. Thats the best thing you should go for. So talk to your doctor about these doubts and follow the advise. If there is need of any medical treatment you will be advised after examining it. hope this helps. Feel free to contact if you have any queries.Wish you good health always,,