Many deodorants use a combination of many, not just one, toxic chemicals, including (but not limited to) aluminum, propylene glycol, TEA/DEA/MEA, FD&C colors, talc, and parabens. These can be causes or catalysts for breast cancer, numerous allergies, and even Alzheimer's disease and associated neurpathies. Research is indecisive about whether or not there is merely a correlation as to the heightened incidence of these diseases in users or if they are the direct cause. Regardless of which of these scenarios proves to be real, both point towards the detrimental effects caused by the toxins in deodorants.
Talc
Talc is a mineral that is used in many products throughout the beauty industry to absorb moisture and add color to products. It is a well known carcinogen because it has asbestos-like fibers found inside as impurities. It is important to note that although society is incredibly outraged with building code regulations of the past not controlling asbestos levels, we are actively consuming beauty products in which the asbestos content is not regulated. Since this asbestos concern looms in the concentration of talc, there is no safe way for a consumer to check the concentration of asbestos in talc products. You are better off staying away from it rather than risking the usage of this irritant and carcinogen. Inhaling these fibers can cause lung cancer, an asbestos-specific restrictive lung disease, and myriad of other lung-related disorders.
Colors
The chemical colors used in the food, drug and cosmetics industry which are so-called "approved" for mass marketing by the Food and Drug Administration are classified as FD&C. It is important to note that these are entirely man-made and synthetic, they are not naturally occurring colorants even though your beauty products and deodorants might suggest that they are. The 'green apple' or 'fruit fusion' flavors you are smelling and the colors you are seeing were mimicked in a lab to look and smell exactly like those you would find in nature. These often cause allergic reactions in people (some people are allergic to a particular dye) and have long been suspected as being carcinogenic because they are derived from strange substances such as coal tar.
TEA/DEA/MEA
These chemicals are solvents used in beauty and makeup products such as shampoos, conditioners, and skin creams because of their ability to cleanse. The function of a cleanser comes from their ability to adjust acidity and they are used to create salts which are then parlayed into cleansers. DEA comes from coconuts and can be found in pesticides. Long-term health effects are allergic reactions, immune-system damage, and liver/kidney tumors. This is just an example of one of their effects but they are all damaging and detrimental to human and animal health.
Propylene Glycol
If the name of this toxin is familiar to you it's probably because you've come across it in your everyday life in the form we're used to: anti-freeze. This chemical keeps substances from becoming dry and is therefore categorized as a humectant. The beauty industry has included it in deodorants for profits because it would stop their products from being adversely affected by temperature changes. There's a laundry list of diseases it can cause such as kidney/liver damage, neurological disturbances, skin rashes, and depression. It's no surprise that inhaling what you would put in your car can so adversely affect your body.
Parabens
These synthetic chemicals, found in almost every single deodorant out on the market (unless they are marked otherwise), can seep through the sensitive armpit's pores and increase the risk of breast cancer. This is known because the concentration of parabens is found to be higher than normal in many tumors found in breasts. The chemical nature of parabens is that they are copycats of estrogen and have similar functions in the body. If you are a woman, it is bad to be intaking more estrogen than your body requires as this is associated with higher breast cancer risk, and if you are a man you can be adversely affected by this estrogen as well because it will offset the hormonal estrogen to testosterone balance. You can spot these in your deodorant if you see names that end in -paraben (such as butylparaben, propylbaraben, and many more) and are used as preservatives widely in the beauty industry so that the products don't expire quickly. 
It is important that we are educated about these substances and do not actively purchase products that we know are poisoning us in time. If we allow the cosmetics and so-called health industry to release products with these chemicals which become fast-selling profit-boosters, they will never cease to release toxic waste under the guise of self-improvement. So go green and seek deodorants that aren't full of all of these chemicals to put on your sensitive armpits, after all, if you don't have your health you can never be beautiful. Stick to brands like Crystal naturally fresh deodorant and pay more for your deodorant so you're not forced to be smearing your 'pits with a chemistry lab.
