What is deep conditioning?
The goal of deep conditioning is to strengthen dry hair and prevent breakage. To deep condition you must use a conditioner that contains ingredients that can patch or absorb into the hair strand. Examples of penetrating ingredients include coconut oil, hydrolyzed protein, amino acids, cetrimonium bromide, panthenol and some silicones.
Does deep conditioning require heat?
No, it's a common myth that deep conditioning requires heat. If a conditioner works with heat its instructions will tell you to apply heat for a specific amount of time. Heat will only increase the effect of a conditioner if it has been formulated with certain ingredients. Conditioners that require heat don't work better than conditioners that tell you to apply and rinse after a few minutes. It all depends on the ingredients.
I like sitting under the dryer. Is there any harm?
Unfortunately, sitting under a bonnet dryer for long periods of time with conditioner in your hair can cause harm. The instructions on your conditioner tell you the safest way to use the product. Studies show that preservatives and other chemicals in cosmetic products can cause eczema and a type of alopecia called telogen effluvium.
We're used to thinking of eczema as a skin condition that runs in families, but frequent exposure to cosmetic chemicals can cause a type of eczema called "acute contact dermatitis". Symptoms of acute contact dermatitis include itching, bumps, tenderness, and dry patches. Studies show that acute contact dermatitis on the scalp leads to a form of short-term alopecia called telogen effluvium. The condition causes excess hair shedding for up to 6 months.
When you leave a conditioner on longer than the recommend time you may be increasing your exposure to cosmetic chemicals that have been linked to eczema, alopecia, and more serious health problems like cancer. Adding heat increases your exposure.
Can I sit under the dryer if I only use natural/organic products?
It will always be safest to follow the instructions on your conditioner. Just because a product is labeled "natural" or "organic" doesn't mean it's safer than anything else. Some natural ingredients cause more allergy problems than synthetic ingredients. There are also loopholes in FDA guidelines that allow manufacturers to omit ingredients from the label. The manufacturer is the only one who knows exactly what's in the container and whether it's safe or not to use the product with heat.
I think I have contact dermatitis on my scalp and excess shedding. What should I do?
1) Make a decision today to follow the instructions on your products. Don't leave in rinse-off products and don't let rinse-off products sit on your scalp for longer than instructed.
2) Visit a Dermatologist or Trichologist for a scalp evaluation if possible.
3) Don't scratch your scalp when it itches. Micro-cuts on the scalp can lead to bacterial infections.
4) Be patient. Itching, bumps, and the other symptoms of acute contact dermatitis usually go away within 4 weeks after the exposure stops. Excess shedding due to telogen effluvium should stop within 6 months.
5) For extra softness and easier detangling when you wash your hair, do a pre-shampoo oil treatment each week.
Updated January 24, 2011

I checked your links, and none of them were for the claim that you do not need heat to penetrate the hair shaft. Can you point me to your source?
Hi Newhere, please take a look at this article ... http://hairliberty.org/black-hair-care/articles/hair-care-secrets/deep-conditioning.html and its comments. I don't think there is a source that says "heat is not required to penetrate the hair shaft" because whether or not heat is required depends on the formula of the conditioner. Water penetrates the hair shaft without heat. Other things can too. Some conditioners require heat, most don't. I hope that helps!
There seems to be some suggestions that using with heat can decrease the amount of time that the conditioner needs to be on the hair, and that the same benefits will occur with room temp application for longer times.
Deep conditioning appears to have a lot of controversy and discussion, but it may be that the most important thing to keep in mind is to 1) follow the instructions on the bottle as was stated in this article and 2) use methods that tend to work best for your hair.
Thanks for the post!
- Crystal
http://www.ishimma.com
I was wondering your thoughts on whether there are different DC approaches that should be taken for low porosity hair vs. high porosity hair? What about fine hair vs. coarse hair?
Hi Nikki,
The curlier the hair, the higher the porosity. Low porosity hair doesn't require deep conditioning to prevent breakage. High porosity hair needs extra conditioning from products labeled "dry", "damaged" or "color-treated". Regarding fine vs. coarse hair, fine hair requires more protein and humidity blocking ingredients because it has less cuticle layers than coarse hair.