Pomeranians grow rapidly through puppyhood, then their growth slows at around 10 months of age. They are considered an adult at one year, but may continue to grow until the 18-month mark.
Sometime around the four- to six-month mark, Pomeranian puppies go through a phase Pom owners affectionately refer to as the 'puppy uglies.' Their fluffy puppy coat sheds drastically in order to make way for their adult double coat. When this happens, they are often left with a scraggly, patchy coat of fur. No Pomeranian is immune, though some may have it easier than others.
Extra brushing and regular bathing during this time will help the process along. Poms may be more susceptible to cold temperatures and a coat or sweater may be necessary to prevent a chill.
During this puppy shed, coat color or markings may darken, lighten, or change entirely. The color change may be barely noticeable, but more obvious changes are possible—such as brown fur turning to cream or parti coloring appearing. The 'uglies' phase usually lasts until one year of age, when the adult coat finishes growing in.
Abnormal hair loss after one year of age may be attributed to 'alopecia x,' a disorder that causes hair loss in Pomeranians and other breeds. This symmetrical pattern baldness is also called 'black skin disease' because the skin may change color. Treatment does not always reverse the hair loss attributed to the condition, but it is not harmful and the hair loss is not contagious.
Occasionally, Pomeranians that are larger—closer to the size of their Spitz ancestors—are born in a purebred litter. If a Pom tops 10 pounds they're considered a 'partial throwback,' and at over 14 pounds they're referred to as a 'throwback' Pomeranian. This throwback gene is unpredictable and can't be bred for. A litter of otherwise tiny Poms may include a single puppy with the throwback gene. These Pomeranians offer the same personality as their smaller counterparts, and they do not suffer from an increase in health concerns. Throwback Poms are not accepted in the show ring as they are outside of breed standards, but may excel at agility or other competitions.