For anyone thats interested in Cat Acne, here is the info I was given

Feline acne is probably more common than is generally appreciated, as most cases are mild and pass unnoticed. More severe cases, however, may respond slowly to treatment and seriously detract from the appearance of the cat.

Two main types of gland are found in the dermal layer of the skin of the cat - the sweat glands and the sebaceous glands. Most of the sebaceous glands are associated with hair follicles and produce an oily secretion, sebum, which waterproofs the hairs and maintains the suppleness of the skin. In addition, a collection of much larger sebaceous glands are found on the chin, the lips, the dorsal (top) surface of the base of the tail and also the eyelids, prepuce and scrotum. The collection of glands under the skin in the chin area is sometimes referred to as the submental organ and the glands around the base of the tail are known as the supracaudal organ.

The oily secretion of these larger sebaceous glands appears to have a role in territorial marking and cats will repeatedly rub their chin, lips, temporal area and base of tail over certain objects. In time the secretions build up on favourite marking objects and may be seen as black, greasy patches. Cat owners may have noticed that they are 'marked' by their pets on returning home. Cats will also often mark certain objects at feeding time.

Overactivity of the submental organs is a relatively common finding and is seen as excessive greasiness of the overlying fur and skin. This is particularly noticeable on the chin of white or pale coloured cats and appears as a yellow, greasy discolouration. There may also be flecks of black, greasy materialonthe chin which may bemistaken for flea dirt; this is sometimes called 'cruddy chin'