There is so much crap out there... What do you look for?
100% pure henna leaf powder. *A fresh crop. **Properly stored in a deep freezer. Powders should be vacuum sealed and in light-proof packaging. No added dyes (plant material or synthetic chemicals), preservatives, metallic salts, not irradiated. Organic is best. Well sifted.
Almost anything that can be purchased in a retail store. It might be pure henna plant powder, but it hasn't been stored properly, so it's dying powder is uber low. Henna powders sold in stores are usually slow shipped (6 weeks to 6 months on a boat), sit in warehouses for months & can sit on the shelf for years.
Really, this should be in with the "Ugly": The Mehndi Oil that is usually sold with henna powder kits in stores. This is the uber cheap alternative to expensive, natural essential oils often used in henna paste. They are a chemical cocktail of unlisted ingredients - definitely not safe.
Pre-made henna cones from the middle east. I'm sure you've seen them: usually large, brightly coloured foil tubes with pictures of henna'ed women on them. They are sold online & in stores (usually middle eastern stores or eclectic, free spirit shops). Not only is the henna old & the dye content pathetic, but those cones of chemical torture have nasty chemicals, preservatives & synthetic dyes added, like kerosene oil, gasoline oil, and the super toxic PPD.
Those blue & white boxed henna hair dyes commonly found at health food stores (ack!) is not only old, but full of metallic salts. That's why most hair stylists think that henna'ed hair can't have chemical processing at the salon.
BLACK HENNA. There is no such thing as black henna. Thank goodness Health Canada had the common sense to make this stuff illegal. Fake ‘Black Henna’ is concentrated para-phenylendiamine (PPD) based hair dye. This is illegal to use on the skin in Canada because of its severe toxicity: it is known to cause tumors, organ failure, permanent scaring, muscle deterioration, etc... If you see someone using this stuff, report them & don't let them touch you!
** Why is a fresh crop important & why store henna in the freezer?
Henna is a plant: the leaves have been harvested, dried & ground into a powder. Like any plant, once it's been picked, the nutrients in that plant start to die off. With henna, the lawsone dye starts to die off just like any other nutrient in the plant. In the henna world, we call that lawsone 'demise." Think of lawsone dye as a vitamin: as soon as a strawberry is picked, the vitamin C content is compromised. Leave that strawberry on the counter or in the fridge for 2 weeks, there won't be much vitamin C left. That's similar to what happens to the lawsone in henna. The only way to stall lawsone demise is to store the henna powder (and dye-released henna paste) is in the freezer.
Lawsone is a tenacious dye -even old powder that's been sitting on a craft store self for 2 years will give a light orange stain, but that's certainly not what we want.