Papules are pink or red colored pimples that are sensitive and painful due to inflammation caused by the P. Acnes bacteria accumulating in the clogged pores. Although they are usually smaller than 5mm, their borders are not clear. Papules often coalesce to form a rash on the skin.
Pustules are inflamed, tender and painful formations like papules. Unlike papules, there are yellow-white inflamed vesicles in their centers. While it may be tempting for many to burst the inflamed vesicles, bursting the pustules will cause them to increase in number and cause the problem to grow.