Titanium dioxide in cosmetics: what are the risks?

What is known about dermal exposure and skin penetration of titanium dioxide?

The titanium dioxide is an essential ingredient in many skincare formulations, with photoprotective properties against UV radiation and a role in powder and cream formulations. A major concern is its interaction with skin, including its capacity to penetrate the skin’s various layers.

Before reviewing specific study results, recall that skin structure serves as an effective natural barrier that limits absorption of many substances. This section examines the various exposure routes and evaluates the potential safety implications of this ingredient.

The absorption of titanium dioxide through healthy skin.

The titanium dioxide in non-nanometric form is common in skin care products because of its established safety: it remains on the skin surface and does not penetrate the living layers of the epidermis. However, the nano-TiO₂ form raises more concerns because its size may enable deeper skin penetration.

The Scientific Committee on Consumer Safety (CSSC) reviewed more than 20 studies between 2013 and 2014 on TiO₂ absorption (nano and non-nano) through the skin. Results show that, regardless of form, TiO₂ remains on the skin surface, with minor penetration into the stratum corneum for nano-TiO₂ and no evidence of penetration into the viable epidermis or dermis.

Other studies in vivo and in vitro on human skin have also suggested that nano-TiO₂ can penetrate deeper into the skin when formulated in an oil-based dispersion. However, an oil-in-water emulsion, where titanium dioxide is dispersed in the aqueous phase, prevents this penetration. Another study on minipig grafts suggested deeper nano-TiO₂ penetration through intact normal epidermis, although it was not significant.

Moreover, applying a cream to minipig skin for about one month showed no apparent adverse effects on the animal’s skin, such as irritation. Other studies found that nano-TiO2 does not penetrate beyond the stratum corneum when combined with cetyl phosphate, manganese dioxide, and triethoxycaprylylsilane in topical formulations. A 2016 review by theAustralian Therapeutic Goods Administration confirms that penetration is limited to the stratum corneum, although one study observed slight penetration after repeated application of sunscreen containing nano-TiO2.

According to the CSSC, nano-TiO₂ and non-nano-TiO₂ in sunscreens pose no health risk when applied to the skin at concentrations up to 25%.

Potential penetration of titanium dioxide into the bloodstream?

A study assessed dermal penetration of titanium dioxide in minipigs. Twelve animals received 5% non-nano or nano titanium dioxide in a sunscreen. Formulations and controls were applied to the skin at 2 mg of cream per cm² four times a day, five days a week, for four weeks. Skin, lymph nodes, and liver were sampled to measure titanium dioxide content. Levels in lymph nodes and liver of treated animals did not exceed those observed in controls.

These initial data suggest that TiO₂ does not enter the bloodstream.

And what about titanium dioxide absorption through compromised skin?

The CSSC reviewed five studies on titanium dioxide penetration under compromised skin conditions (shaved skin, sunburn, psoriatic skin) in mice, pigs, and humans. These studies found that titanium dioxide (micron-sized and nano-sized) did not penetrate compromised skin to a greater depth than healthy skin. Although nano-TiO₂ reached deeper regions of the stratum corneum in psoriatic skin, it did not enter viable cells in either skin type. Subsequent research confirmed these findings, showing limited penetration of nano-TiO₂ in intact skin or skin with slight damage. A study on human skin exposed to UVB rays detected nano-TiO₂ in viable cells, but this was observed in two volunteers using a single sunscreen formulation.

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Inhalation risks of titanium dioxide?

It is well established that nano-TiO₂ are more toxic than the micrometric form. Nano-TiO₂ can be inhaled when present in spray or aerosol products, such as certain mists, although their use in these products has been banned since 2009 by EU Cosmetic Regulation (EC) No. 1223/2009. Inhalation of these particles can cause respiratory irritation and lung inflammation, leading over time to pulmonary dysfunction, fibrosis, and cancer risk, depending on their nanoscale form and properties (size, shape, crystallinity, etc.). The risks are associated with occupational exposure or cosmetic aerosols.

However, these situations remain uncommon in home settings and prolonged or high-dose exposure is more problematic. For short-term inhalation, a threshold of 3.5 mg/m³ applies to spray use and a threshold of 17 mg/m³ applies to repeated inhalations over an eight-hour workday. Studies show that inhaling concentrations up to 35 mg/m³ does not cause chronic lung overload.

What are the risks of ingesting titanium dioxide?

In recent years, concerns have emerged about the use of titanium dioxide after it was banned as a food additive (E171) in some countries. However, it’s essential to distinguish its use in foods from its use in cosmetics, where the quantities and contexts of exposure differ significantly.

Available studies to date using in vitro and animal models report negligible or no absorption of titanium dioxide—whether nano or non-nano—by the gastrointestinal tract after oral exposure. The quantities of TiO₂ used in these experiments exceed those associated with accidental ingestion through lip products such as lipsticks. Current data also show no clear evidence of carcinogenic or genotoxic activity linked to oral titanium dioxide intake.

It is crucial to distinguish exposure contexts assessed by different regulatory agencies. The Scientific Committee on Consumer Safety (CSSC) evaluates risks related to titanium dioxide in topical products, which are not intended for ingestion. Any ingestion in this context is accidental and the quantities involved are minimal. By contrast, the European Food Safety Authority (EFSA) evaluates risks related to titanium dioxide as a food additive, where exposure levels are much higher because it is intentionally consumed in food.

In summary, although uncertainties remain, current data do not justify significant concern about accidental ingestion of titanium dioxide in skincare products, due to the low quantities involved and lack of clear evidence of toxicity. However, further research is needed to clarify long-term effects and reassure consumers.

Nano-TiO₂ poses a higher risk than micrometric TiO₂ because of its greater penetration into tissues and cells.

Effects of titanium dioxide on pregnant or breastfeeding individuals?

No specific prohibition or warning exists regarding the use of skincare products containing titanium dioxide during pregnancy or breastfeeding, including lip products. Regulatory authorities consider the levels of titanium dioxide in these products safe for consumers, even in case of accidental ingestion.

However, some experimental studies have explored the potential effects of titanium dioxide on pregnancy and postnatal development. For example, one study in pregnant rats administered 100 mg/kg per day of nano-TiO₂ by oral administration during gestation. This dose exceeds any human exposure from skin care products, where accidental ingestion is minimal. Results showed minor physiological disruptions in mothers, such as changes in antioxidant enzymes and metabolic markers. Titanium dioxide accumulated in organs including the liver, brain, and placenta.

In offspring, effects on postnatal development were observed, including variations in body weight, delays in sensorimotor maturation, and changes in motor reflexes. These observations suggest a potential effect on the central nervous system, although no major malformations or structural abnormalities were detected in fetuses.

It is crucial to note that these results derive from animal studies using doses that exceed those encountered in everyday life.

For example, accidental ingestion of titanium dioxide from lip products is extremely low and represents only a small fraction of the dose tested in these studies. Moreover, human data on this subject are limited and do not show conclusive evidence of a risk for pregnant or breastfeeding individuals.

Essential facts about the health effects of titanium dioxide.

Current studies suggest that titanium dioxide remains on the skin surface, with limited penetration into the skin layers, even on compromised skin.
Risks of inhalation and ingestion, although concerning, appear primarily linked to occupational exposures or specific uses, such as sprays or food additives.
In the current state of knowledge, titanium dioxide in cosmetics is considered safe when used in accordance with existing regulations.