A good shampoo for maintaining healthy hair typically avoids certain ingredients that can be harsh, stripping, or potentially harmful to the hair and scalp. Here are some ingredients you might want to avoid or limit in your shampoo:

1. Sulfates (Sodium Lauryl Sulfate and Sodium Laureth Sulfate): These are strong detergents that create a rich lather but can strip natural oils from the hair and scalp, leading to dryness and irritation.
2. Silicones: While some silicones can provide softness and protect hair from heat damage, they can build up over time, weighing down fine hair and requiring harsher cleansers to remove.
3. Parabens (Methylparaben, Propylparaben, etc.): Parabens are preservatives used to extend the shelf life of products. They have been controversial due to concerns about potential hormonal disruption, though research is ongoing and inconclusive.
4. Alcohol (Especially Isopropyl Alcohol and Denatured Alcohol): Certain alcohols can be very drying to the hair, stripping away moisture and causing brittleness.
5. Synthetic Fragrances: These can be irritants for sensitive skin and scalps, causing itching, redness, or allergic reactions. Look for shampoos with natural fragrance sources or labeled "fragrance-free."
6. Polyethylene Glycols (PEGs): PEGs are used as thickeners and solvents in cosmetics but can potentially contain harmful impurities like ethylene oxide and 1,4-dioxane.
7. Mineral Oil and Petrolatum: These ingredients can coat the hair, preventing moisture from penetrating, and can also clog pores on the scalp.
8. Diethanolamine (DEA), Triethanolamine (TEA), and Monoethanolamine (MEA): These chemicals can react with other ingredients in the shampoo to form nitrosamines, which are potential carcinogens.
9. Formaldehyde-Releasing Preservatives: Used to prevent bacterial growth, these can release small amounts of formaldehyde over time, which is a known irritant and carcinogen.

When choosing a shampoo, look for products that are labeled as "sulfate-free," "paraben-free," and "cruelty-free." Opt for formulations with natural or organic ingredients, and consider your hair type and specific needs (e.g., color-treated, dry, oily, or sensitive scalp). It's also advisable to read ingredient lists carefully and do a patch test if you have sensitive skin.