Are bicolor cats rare, friendly, hypoallergenic?

Tuxedo cats are bicolor cats. This is my darling deceased female. Image: MikeB

Bicolor cats are cats with a coat of two (as in 'bi') colors: white and another colour such as black or ginger. And the 'other colour' can have tabby markings. 

They can be moggies (random-bred cats) or purebred, pedigree cats. It does not matter which. They are common and therefore not rare. Neither are they hypoallergenic but they are friendly if they've been socialised properly and treated well.

No domestic cat is hypoallergenic as the Fel D1 allergen is produced by all domestic cats. Purina LiveClear works pretty well to make a cat acceptable to a person allergic to cats.

'Hypoallergenic' means not producing an allergic reaction in people. About 10% of people are allergic to cats.

The white fur in bicolor cats is caused by the presence of the piebald aka white spotting gene, which affects the migration of pigment producing cells (melanocytes) in the skin during the development of the embryo. 

Where there are no melanocytes there is no melanin in the hair strands. White fur does not contain pigment namely melanin.

It is white because the light from sun or room light passes through it. White light is a mixture of all the colours of the rainbow.

Melanin is a brown/black. If it is diluted, black becomes blue grey and red becomes cream and so on.

The experts rate bicolor cats from 1 to 10 depending on the amount of white fur. Level 1 is black and no white fur while level 10 is all-white. The cat in the picture is about level 4.

If you have a question, ask in a comment and I'll be pleased to respond. I always check comments as I get so few! :)

Level 9 bicolor Cornish Rex. Image in the public domain.

My cats mouth is "spotty" and looks strange to me. I'm concerned.

The picture comes from Reddit.com again - a good source of questions about cat appearance and behavior. The problem stated in the title is one which crops up from time to time on the Internet. It can look a little concerning because cat owners expect the inside of their cat's mouth to be pink because the mucous membrane there is normally evenly pink. 

Pigmentation in the mucous membrane of a cat's mouth. Image: Reddit.com

But sometimes the cells of the mucous membrane can be black because of the production of melanin which is the same pigment which colours the hair strands. It's all perfectly normal. They look a bit like freckles inside the mouth. This is not a health problem in any shape or form. Sometimes there are large blotches of black mucous membrane and sometimes you might see little dots of pigmentation along the gum line. No problem.

It is nice that the owner of this cat who posted the picture on the Reddit.com website is asking if other people are concerned about the appearance of her cat which she must love and care for well.

On a slightly different topic, it seems that the interior of his mouth is pretty healthy too! Sometimes you see some quite bad inflammation of the gums due to gum disease which in turn is due to calculus building up around the gum line. 

Tragedy as female cat suffers catastrophic reaction to general anesthetic.

This contains bacteria which causes the inflammation. It is very hard, as we all know, to clean a cat's teeth! That's why they end up going to the veterinarian for teeth cleaning which, you might already know, carries a health risk because they have to anaesthetise the cat and there is an approx. 1 in 400 chance of the anaesthetic damaging the cat's brain which can render them blind and even kill them (click the link above for a tragic example).

Cat develops a dead straight blonde fur line on her black fur overnight. Why?

This is the question on Reddit.com: Binx has (overnight) developed a dead straight line of blonde on her back. Any ideas?

Black cat with blonde stripe on her back which developed rapidly. Image: u/FyldeCoast on Reddit.com

There is obviously no certainty that I am correct. It is a kind of guess based on little to go on. If you have a better idea please comment. It would be great if you did 😃.

RELATED: 2 examples of feline vitiligo (leukoderma).

This is my answer

It looks like it could be vitiligo. It is harmless. Antibodies attack the melanocytes (pigment producing cells in the skin in the hair follicle bulb). The melanocytes are destroyed and no longer produce melanin, a dark pigment producing black fur. This leads to fur without pigment in a localised area. The hair strands in that are just keratin and therefore semi-transparent having the appearance of being off-white. The white area may expand. Sometimes cats with vitiligo turn from black to white! Studies indicate that changes in the immune system are responsible for the condition and that both underlying genetics and environmental triggers are involved. Now you'll tell me some bleach dripped onto her back 😊.

Are hairless cats really hairless?

No, so-called "hairless cats" are not truly hairless because various parts of their bodies maybe nude but the remainder e.g. the muzzle and the feet (often) are covered by fine down, fuzzy hair. Sometimes hairlessness progresses with age. There is a fine covering in the young adult cat which gradually disappears leaving a bare, wrinkled skin over much of the body of the full-grown adults.

Bicolor Sphynx. The fine down hair strands in the hind legs are
pigmented I believe, which is why there is a dark patch and the tail
 is dark too. This is melanin in the down hair strands.

There is a bit of discussion about whether hairless cats can have a pattern on their skin. You do see 'bicolour' Sphynx cats with the two colours being the skin colour and the other colour being an inky darker colour. 

I had thought that the darker coloration was due to the pigment producing cells, the melanocytes, colouring the skin but I now believe that this is due to fine down hairs having the coloration that the cat's genetics gives it. The melanin in the hair strands being produced by the melanocytes.

To be clear, if you see a bicolour Sphynx or any other hairless cat what you are seeing is hair strand coloration. The point is that you can barely see the hairs because they are very fine and short, being the down or undercoat.

Altering the Color of Siamese Cats

We know that the pointing of Siamese cats is caused by heat sensitivity. The warmer the environment the paler the color. The extremities of a Siamese cat are cooler hence darker than the central part of the body.

Reason For Siamese Cat Pointing

To recap: at normal body temperatures the enzymes present in the Siamese cat are unable to produce melanin (a pigment) but at lower temperature the enzymes are able to perform their normal function and produce melanin. At the extremes of the cat the skin is cooler and so those areas have darker fur (pointing).

When the kitten in born they are white because they have been in the warmth of their mother's womb. The pointing develops and is then fixed for that cat.

On the basis that the paleness of body color and darkness of the pointing becomes fixed at a certain point in the kitten's development, it appears that it is possible to deliberately alter the color of an individual cat by adjusting the ambient temperature under which the cat is raised. Just a thought.

Personalized Siamese Cat

It has been suggested that you can create a personalised Siamese cat. I am not suggesting that you do this but it is interesting. You gently shave your initials into the Siamese cat's fur (remove the fur in the form of your initials) and while it grows back you cool the area you have shaved. The new fur should be darker and therefore your initials will be visible in the fur for the life of the cat. Obviously the area where you do this is the central (paler) part of the body.

It sounds strange and I don't want to start a fad or cult. But the science behind the Siamese cat pointing supports the idea that it is possible to create a personalized Siamese cat!