Salicylic acid, willow bark, BHAs, etc

[Guest guest]

It's a confusing topic. This is how I think of it: Salicylic acid is

the main ingredient in aspirin, which as we all know is an excellent

anti-inflammatory agent, but salicylic acid on the skin can also do

more, depending on its concentration and pH.

All acids (and bases) are potentially irritating to the skin; most

comforting are pHs closest to the skin pH. In general, the higher the

concentration of any acid, and/or the lower the pH of any solution,

the greater the risk it will irritate the skin. The relationship

between concentration and pH of an acid is this: unless a

neutralizing base is added to the product, the higher the

concentration of an acid, the lower the pH.

Depending on its concentration and on the pH of the solution/cream,

salicylic acid is appropriate for different uses. Topically,

salicylic acid is thought to be anti-inflammatory at concentrations

of 0.5% and above; it is keratolytic (exfoliative, dissolves dead

skin cells) at concentrations of about 2% to 6% as long as the pH is

below 4; it is used to remove warts (potentially destructive to

living tissue) at concentrations over 6%, and at an equally low pH.

That salicylic acid requires such a relatively low concentration (one

study found 1.5% comparable to the more typical 8% of other

exfoliates) is a real advantages; that means it can exfoliate at a

relatively higher pH so it is considered milder than other

exfoliatives. Another advantage is that salicylic acid gets into

pores and cleans them out/be directly anti-inflammatory, both of

which are especially good for people with acne rosacea or acne

vulgaris. But -- and this point is key -- it is an exfoliant only at

the proper concentrations and in acid solutions; if the pH is over 4,

at any concentration, it does not exfoliate, though -- and this is

also key -- it may still be anti-inflammatory.

Willow bark (willowherb) contains the precurser to salicylic acid,

it's one of the plants from which aspirin is derived, so it is

chemically related to salicylic acid. But here's the key point: it

isn't an acid, so it doesn't risk that potential skin irritation. Of

course, it isn't an exfoliant and it doesn't have salicylic acid's

anti-inflammatory properties either, although from what I've read

most herbalogists and pharmacologists believe topical willow bark has

its own anti-inflammatory properties; it does not need to be

converted into an acid (salicylic acid) on the skin (as it does when

taken orally) to exert an anti-inflammatory effect topically.

BHA is a term often by the cosmetics industry as synonymous with

salicylic acid. Together with AHA, they are chemical terms that have

been misused by the cosmetic industry as a buzzword to identify a

type of exfoliator. Both refer to the placement of an -OH group

within the acid, but exfoliation doesn't necessarily require the

chemical structure identified by the terms AHA and BHA.

Commonly, the exfoliators identified by the cosmetics industry as AHA

are stronger and don't penetrate pores as do BHA (by which they mean

salicylic acid). It would be helpful if the cosmetic industry

reserved BHA for salicylic acid at or above the needed concentration

and at or below the needed pH, so we would know if that preparation

can be used as an exfoliant. But that's not the case, the use of the

term BHA has nothing to do with the product's ability to exfoliate.

That depends totally on the concentration of salicylic acid and pH of

the product.

Regarding Total Turnaround Cream, like many many products, it has

salicylic acid listed in the middle of its disguistingly extensive

ingredient list, but more important, Total Turnaround Cream, again

like many products, has a pH well above 4, so by definition it isn't

an exfoliant whatever Clinique says. Is it anti-inflammatory? I

suspect so, but I have no proof, it may just be inert. Is it

irritating? It's not an exfoliant or even acidic so I wouldn't

think so -- except for the caveat that anything can be a potential

irritant, as we all know.

Anything that chronically irritates the skin will tend to thin it,

perhaps because chronic irritation interferes with normal collagen

production. I've not heard that salicylic acid has a unique property

that is harmful to rosaceans; from everything I've read, quite the

contrary (given the proper concentration and pH used).

Hope that helps.

Marjorie

Marjorie Lazoff, MD