You should avoid any type of product that contains synthetic fragrances, petroleum products, preservatives and solvents. Most products containing miner oils are bad for your skin as well. Since mineral oil can dry out your skin and cause other irritation that isn't necessary. Coconut oil is a good substitute for products containing mineral oils.
Two of the most common preservatives used in beauty products are Diazoliddinyl Urea and Imidazolidinyl Urea. These two products have been shown to cause dermatitis. Dermatitis is a serious skin infection. Allergens can cause you to have rashes and cause dermatitis if you are allergic to either of those preservatives. It also is a term used for eczema. It has the appearance of a normal skin rash, to red bumps, to massive blisters, and severe itching. The swelling and itching of lesions caused from dermatitis is a very unpleasant appearance and can be very painful.
Some other substances that should be avoided are Propylene Glycol, DMDM Hydantoin, Sodium Lauryl Sulfate, Imidazolidnyl Urea, Parabens and Iodopropynyl Butylcarbamate. A good rule of thumb when buying beauty products is this: if you cannot pronounce it and don't know what it is, you shouldn't be putting it on your skin regularly. Some products use the Latin names of fruits and vegetables that are found in natural skin care products. It is always best to research questionable ingredients as well. Example: Rubus idaeus is a Latin word for raspberry.
To make an example of just a few of these compounds, DMDM Hydantoin is a complex molecule that is used to preserve beauty products because it releases formaldehyde. Formaldehyde has recently been banned for use in beauty products in Europe and Asia because it is thought to be carcinogenic. This chemical is also found in nail polish. I would rather not have nail polish like chemicals on my skin. Sodium Lauryl Sulfate is used in all kinds of soaps and detergents, releases formaldehyde, and is a skin irritant that can cause dermatitis, psoriasis and eczema... which I explained above how awful dermatitis can be. Propane Glycol is used to change the texture of cosmetics and soaps. It causes sensitivity and irritation to your skin and can make you skin look very unhealthy.
Organic soap, lotions, shampoos, and more have less harsh chemicals and ingredients in them that wont effect your skin and body as regular purchasable skin care products. All of the bad chemicals in regular products are less than ideal when used on the skin, especially if used often. When you're buying beauty products, remember to check the labels.