I can sex by colour as I have read about how the genetics of a cat work.
The colour gene is carried on the X chromosone.
Females have an XX and males have an XY.
The father is completely black, therefore carried only the black gene.
The mother is tortie, therefore carried both Black and Ginger genes.

The possible out comes for boys, are all ginger (where they got the ginger gene from mum); or black (where they got the black gene from either mum or dad)

The possible outcomes for the girls are, tortie (where they got the ginger gene from mum, and the black gene from dad); or black (where they got a balck gene from both mum and dad).

This means I know that gingers must be boys, torties must be girls and black (or black and white) can be either.

Just as a note, you can only ever get a ginger female from having a ginger mum and dad. (or tortie mum and ginger dad). And you can never get a tortie male unless there is a defect and he will be sterile.


As for the saliver allergic issue, most people who are allergic to cats actually have a problem with something in the saliver, I know it causes a histamine reaction and something to do with testosterone makes it worse, but I don't know the full detials. The fur is normally only a problem for asthmatics.