1. Formaldehyde:
Source: Formaldehyde is often used as a preservative in cosmetics and personal care products. It can be released over time by other preservatives such as quaternium-15, DMDM hydantoin, and imidazolidinyl urea.
Harmful Effects: Formaldehyde is a known carcinogen and skin irritant. Prolonged exposure can lead to allergic reactions, dermatitis, and respiratory issues.

2. SLS & SLES (Sodium Lauryl Sulfate and Sodium Laureth Sulfate)
Source: These surfactants are commonly used in skincare and personal care products for their foaming and cleansing properties.
Harmful Effects: SLS and SLES can strip the skin of its natural oils, leading to dryness, irritation, and even exacerbating conditions like eczema. They may also cause eye irritation and allergic reactions.

3. Parabens:
Source: Parabens are synthetic preservatives used to extend the shelf life of products.
Harmful Effects: Parabens can disrupt hormonal balance and have been linked to breast cancer and reproductive issues. They may also cause skin irritation and allergic reactions.

4. Phthalates:
Source: Phthalates are often used as plasticizers in cosmetics and personal care products to improve texture and flexibility.
Harmful Effects: Phthalates can disrupt hormone function and have been associated with reproductive and developmental toxicity. They may also cause skin irritation and allergic reactions.

5. Silicones:
Source: Silicones are synthetic polymers used in skincare and hair care products to create a smooth texture and seal in moisture.
Harmful Effects: While silicones themselves are not inherently harmful, they can trap dirt, sweat, and bacteria on the skin, leading to clogged pores, acne, and irritation for some individuals.

6. Triclosan:
Source: Triclosan is an antimicrobial agent often found in antibacterial soaps, cleansers, and toothpaste.
Harmful Effects: Triclosan has been linked to hormone disruption, antibiotic resistance, and environmental pollution. It may also cause skin irritation and allergic reactions.

7. Dioxane:
Source: Dioxane is a byproduct of ethoxylation, a process used to make certain ingredients gentler on the skin.
Harmful Effects: Dioxane is a known carcinogen and may also cause organ toxicity. Prolonged exposure can lead to skin irritation and allergic reactions.

8. Toluene:
Source: Toluene is a solvent used in nail polish and hair dyes.
Harmful Effects: Toluene exposure can cause skin irritation, headaches, dizziness, and damage to the nervous system. It has also been linked to developmental and reproductive toxicity.

9. Diethanolamine (DEA) and Ethanolamine (MEA):
Source: DEA and MEA are used as emulsifiers and foaming agents in skincare and hair care products.
Harmful Effects: DEA and MEA can react with other ingredients to form carcinogenic nitrosamines. They may also cause skin irritation and allergic reactions.

10. Hydroquinone:
Source: Hydroquinone is a skin-lightening agent used to treat hyperpigmentation.
Harmful Effects: Prolonged use of hydroquinone can lead to ochronosis, a skin condition characterized by darkening and thickening of the skin. It may also cause skin irritation and allergic reactions.

11. Oxybenzone:
Source: Oxybenzone is a chemical sunscreen agent used to absorb UV rays.
Harmful Effects: Oxybenzone has been linked to hormone disruption, allergic reactions, and coral reef damage. It may also cause skin irritation and photosensitivity.

12. Mineral Oil:
Source: Mineral oil is a byproduct of petroleum distillation often used as an emollient in skincare products.
Harmful Effects: Mineral oil forms a barrier on the skin that can trap impurities and inhibit the skin's natural functions, leading to clogged pores, acne, and irritation for some individuals.

13. Synthetic Colors:
Source: Synthetic colors are artificial dyes used to enhance the appearance of cosmetics and personal care products.
Harmful Effects: Some synthetic colors contain heavy metals and coal tar derivatives that may cause skin irritation, allergic reactions, and even cancer in some cases.