Dr Charlene DeHaven details which common skincare ingredients to avoid during pregnancy and when breastfeeding
It is understandable that patients who are expecting may be concerned about issues accompanying those special times of life not directly related to the pregnancy or post-pregnancy period. Skin problems, such as acne, tend to be more recurrent and are a response of the pilosebaceous unit to androgen levels,1 and therefore questions may arise about which skincare products can be used safely.
Concern related to topical products depends upon ingredient penetration through the skin to the developing foetus in the case of pregnancy, or to the infant in the case of breastfeeding (lactation). There are a few exceptional ingredients that will be discussed below but, in general, most skincare products are not absorbed through the skin into the body as a whole, therefore not of concern.
Efficiency of the skin barrier
The skin is biologically designed as a barrier and it is quite efficient at ‘keeping things out’, including substances placed on it, and also at ‘keeping things in’, such as bodily fluids. The cornified envelope, the outermost layer of stratum corneum, is particularly impermeable to substances.2,3 As cells of the epidermis move upward during their normal transit from basal layer to stratum corneum, they extrude their intracellular contents and nuclei.
The term ‘cornified’ refers to an almost horny layer, composing the outermost skin that is formed from lipid-rich (fatty) material, from which water has evaporated, leaving a cornified or horny coating that composes our outermost skin. The cornified envelope, if viewed under magnification, would show a horny-looking pattern of flattened skin cells surrounded by lipid-rich material. Furthermore, the epidermis has very few blood vessels compared to deeper layers of dermis. The combination of an efficient skin barrier and lack of vascularity means that topical penetration is difficult (Figure 1).
Figure 1: The graphic above illustrates the efficient skin barrier of epidermis. Note the lack of blood vessels in this area.
Non-systemic design of topicals
Despite an efficient skin barrier, some of the ingredients in high-quality skincare products are designed to penetrate the skin barrier and reach a site of action within the epidermal and dermal layers. Skin penetration in these cases is difficult but not impossible with sophisticated formulation techniques. However, in contrast to medicines, skincare products are generally designed to be ‘non-systemic’ – a term referring to the fact that they are not delivered throughout the body by the circulatory network. Systemically delivered topical products are classified as medicines and fall into a different regulatory category.4
Thus, for most topical skincare products, systemic delivery of ingredients to the uterus and breast does not occur. Some exceptional cases will be discussed below. Because it is almost impossible for the end-user to know specifics about quality control or formulation techniques for individual skincare products, individual ingredients that are even potentially harmful are best avoided during pregnancy and lactation. During these times, even the smallest risk of toxicity related to possible systemic absorption is unacceptable.
For all of these ingredients, the overriding recommendation is for the pregnant or lactating woman to consult her general practitioner and reliably follow his/her specific recommendations for which concern for the patient is sincere.
If a patient misses a favourite skincare product during pregnancy or while nursing, remind them that these times of life are usually short and the use of the product may begin again after only a brief interlude.
Hydroquinone should be considered unsafe during pregnancy and lactation. Its use during these times should be avoided because of potential toxic effects.5
Hydroquinone is widely used throughout the world as a skin lightening ingredient. Hydroquinone fully penetrates the skin barrier, enters the capillary network of the circulation, and is systemically delivered. It has been estimated that 35% to 45% is systemically absorbed following topical use in humans,6 and within a few minutes of skin application, hydroquinone levels are measurable in urine.7 Due to a lack of human studies, it has not been specifically proven that hydroquinone crosses the placenta but its molecular weight is small enough to potentially do so.8
Information about tretinoin is somewhat conflicting. Under these circumstances, avoidance might be the safest option
A single study has been published involving the use of hydroquinone during pregnancy with no increase in adverse events, however, the sample size of pregnant women was small.9 Animal studies have been performed; maternal toxicity and foetal anomalies of weight and bone were shown but these doses were higher than the average human use.10 Even considering the lack of human studies, I believe the use of hydroquinone should be avoided during pregnancy and lactation due to its high absorption through the skin and general toxicity profile.
Vitamin A and tretinoin
Topical vitamin A may be considered safe during pregnancy and lactation.11 However, because obstetricians are so wary of the teratogenic effects of very high doses of oral vitamin A, some will recommend avoiding all vitamin A products, including topical vitamin A, during pregnancy. Conversely, oral vitamin A is available in some countries in prenatal vitamins in doses of 1500 IU.
The absolute amount of oral vitamin A required for teratogenicity is unknown but is most likely in the range of 20,000-50,000 IU, which is far above usual intake or even supplementation. Birth defects have been associated with oral Vitamin A intakes of 25,000 IUs, although causality was not definitely proven. As a result, the Teratology Society recommends that, during pregnancy, vitamin A doses should be below 25,000 IU because of the risk of teratogenicity.12However, as dietary amounts of vitamin A in pregnant adults living in developed countries exceed deficiency amounts, obstetricians do not recommend routine oral vitamin A supplementation.13
Information about tretinoin is somewhat conflicting. Under these circumstances, avoidance might be the safest option. The United States Pharmacopeia Dispensing Information recommends avoiding topical tretinoin during pregnancy.14 Some studies of women taking tretinoin during pregnancy revealed no difference in birth defects compared to women who had not taken it.13 Other sources have noted that birth defects have been found in women using tretinoin, thus providing suggestive evidence that topical tretinoin is a potential foetal developmental toxin14,15 It is difficult to find human data because studies involving humans are very rare, but ultimately, I believe it is best to avoid tretinoin.
Levels of both clindamycin and erythromycin, both common antibiotics used for acne, are not detectable in the circulation following application
Mention should be made of another oral vitamin A derivative, isotretinoin, that is absolutely to be avoided during pregnancy because it is so teratogenic.16 In fact, female patients taking isotretinoin for acne must use a very reliable method of contraception and have regular pregnancy tests for monitoring.17
Both beta hydroxyacids (BHAs) and alpha hydroxyacids (AHAs) are frequently used for acne treatment. Glycolic acid is probably the most frequently used AHA and its concentration, time of application, and overall formula pH may vary widely. All of these parameters will affect absorption through the skin but, even so, systemic absorption would be minimal at best.18 AHAs can be considered safe during pregnancy.19 Animal studies have been conducted with glycolic acid but do not apply to humans because the doses were so high and far out of proportion of anything considered even close to human use.17
Salicylic acid is the prototype BHA and the situation for topical use and potential toxicity in pregnancy or nursing is the same as for the AHAs. No human studies have been conducted but absorption is minimal at best.20 This is in contrast to therapeutic doses of oral salicylates that may be problematic to the foetal cardiovascular system, if taken during the third trimester of pregnancy.21
Below are other ingredients and products patients may frequently use that they may feel concerned about using during pregnancy and nursing.
Benzoyl peroxide is also frequently used topically for acne in varying concentrations. It is generally considered safe during pregnancy and lactation.22
Use of sunscreens is recommended during pregnancy and lactation, as in all other times of life. The physical sunscreens zinc oxide and titanium dioxide are considered safe during pregnancy.21 Chemical sunscreens include two general classes – the PABA (para aminobenzoic acid) derivatives and the cinnamic acid derivatives. Even at doses higher than used in sunscreens, chemical sunscreen actives do not penetrate the skin barrier.21
Topical antibiotics are often prescribed for acne and the occurrence or severity of acne may increase during pregnancy. These topical antibiotics are prescription products and classified as medicines rather than skincare topicals. Short term usage of topical antibiotics are considered safe during pregnancy.23 Levels of both clindamycin and erythromycin, both common antibiotics used for acne, are not detectable in the circulation following application.24,25
Most topical skincare products are safe during pregnancy and lactation due to minimal absorption, related both to an efficient skin barrier and formulation design. A few topical products are exceptions and it is probably best to avoid these during pregnancy and nursing. Importantly, products containing hydroquinone and isotretinoin, and, most likely, tretinoin as well, should be avoided.