Here, the aggregate of properties are peculiar to an individual, where the sum of the attributes distinguish an object from others of the same kind (Oxford English Dictionary).
Essentially, the root for 'individualism' and 'individuality' is individual, which indicates an entity or idea that is not divisible. Although both terms embrace the idea of inseparability, the intentions for both behaviors are very different. While the doctrine of 'individualism' may be tied to the thought of 'egoism' (Wikipedia) which suggests self-serving tendencies, the principle of 'individuality' does not require the sacrifice of self-interest for any other causes.
In summary, it can be argued that 'individualism' is more about an approach to life where individual benefits are paramount and it opposes collectivism where no sacrifice is made. On the other hand, 'individuality' is geared more towards a quality of life which values individual choice and may not entirely be self-serving or self-sacrificing which then creates a certain degree of identity.