Human skin’s most important function is as a defence organ to prevent outside compounds from entering into our body, however it cannot prevent smaller molecules from penetrating.
Our skin is absorbent
Humans have an outer layer of skin, referred to as the corneal layer of the epidermis. This outer layer is just a few micrometers thick with between 5 – 7 cell layers, but effectively forms a barrier that preserves life by protecting our insides from the outside world. Topical creams attempt to penetrate past the epidermal barrier and this is sometimes a challenge when the compounds consist of large molecules.
The 500 Dalton Rule
The molecular weight (MW) of a compound must be under 500 Dalton to allow skin absorption. Larger molecules cannot penetrate the corneal layer.
Interesting things about the 500 Dalton rule are:
- The most common allergens that cause contact dermatitis have a molecular weight (MW) that is under 500 Dalton, and larger molecules are not known as contact allergens. Nevertheless, thousands of molecules have been recognised as inducing contact dermatitis.
Dermatology creams and ointments
- The most commonly used and effective topical drugs in dermato-therapy all have a molecular weight under 500 Dalton.
- Certain drugs for system wide treatment need to be delivered through the skin in order to avoid the liver. Transdermal drugs may include nicotine or hormone patches and of the 7 or more drugs delivered transdermally, all are smaller than 350 Dalton.
Harmful things that creep under our skin
What compounds do you use on your skin that have a molecular weight under 500 Dalton?
Dermatology treatments for psoriasis
Creams that we use topically to treat psoriasis are designed to enter our body systems. While these creams have been tested to treat our psoriasis, their safety risks have not been explored. For example, corticosteroids are highly effective in psoriasis but there is a lack of long-term effectiveness and safety data available on this treatment used for psoriasis. Coal tar creams and lotions that are commonly prescribed for psoriasis have been tested to have little or no benefit in treating psoriasis, yet expose us to the risk of side effects.
Medical researchers warn that a strategy for the safe and effective long-term use of treatments for the maintenance of disease control in psoriasis is urgently needed.
Parabens are used in over 22,000 cosmetics as preservatives, and are known to cause endocrine disruption, including male reproductive toxicity and various estrogenic activity studies. Are these parabens able to enter our body through our skin? Take a look at the size of their Daltons:
Butylparaben 194 Daltons
Ethylparaben 166 Daltons
Methylparaben 152 Daltons
Propylparaben 180 Daltons
For the psoriatic
Step 1: Check your labels for parabens and consider using natural alternatives such as:
- Apple cider to wash skin and hair and maintain our pH acid mantle
- Natural oils to moisturise
- Magnesium chloride bath soaks
Step 2: Begin to wean yourself off dermatological creams and ointments that penetrate our body systems and put us at risk of side effects, and begin to heal from the inside out. Psoriasislife Mag will continue to provide many well researched articles to help you achieve this.
Bos JD, Meinardi MMHM. The 500 Dalton rule for the skin penetration of chemical compounds and drugs. Exp Dermatol 2000: 9: 165-169.
Kalb RE et al. Risk of Serious Infection With Biologic and Systemic Treatment of Psoriasis. JAMA Dermatol, 2015;151(9):961-969
Topical therapies for the treatment of plaque psoriasis: systematic review and network meta-analyses https://www.ncbi.nlm.nih.gov/pubmed/19101832