Pimple On Back Of Ear. The Merck Manual website notes that seborrheic dermatitis causes scaly pimples to form. This occurs commonly with blind pimples.

Similar to pimples occurring in some body areas pimples behind ears are caused by blocked skin pores combined with sebum overproduction. Acne lumps behind the ear. A pimple may develop on the earlobe that when you attempt to pop nothing oozes out.
Of course there are some other causes contributing how prone someone is to pimples and acnes such.
While pimples are less likely to develop there due to the areas relative isolation it can. The pimples in the ear are very painful due to the lack of fat in your ear. Stress can cause excessive sweating andor changes in your hormones which contributes to oil production. Pimples in the ear can occur in all shapes and sizes.