Is green algae safe?

The potential hazards of green algae in topical application.

Few, if any, studies have been conducted on the exploration of potential dangers of using green algae on humans. Overall, these organisms are safe to use. However, some points can be clarified. Due to the lack of scientific data on the subject, we cannot affirm whether the topical application of green algae could pose problems.

However, a concern could arise from their potential comedogenicity. Indeed, algae in general could pose a risk of comedogenicity. They would penetrate the pores and accelerate the growth of micro-comedones. It is nevertheless important to note that comedogenicity is not an exact science.

• No study has specifically demonstrated a comedogenic effect of green algae;

• Most of the green algae found on the market are used in the form of extracts, which are far too small to "clog" the pores;

• What is "comedogenic" for one person may not necessarily be so for another;

• The fact that an ingredient is considered comedogenic does not automatically mean that the product containing it is as well.

The potential hazards of consuming green algae orally.

Regarding their oral consumption, studies conducted on the subject have shown no toxicity of green algae. The administration of chlorella powder (a type of green algae) to mice has demonstrated no toxicity, nor any adverse effects that could compromise its use as a nutraceutical and/or dietary supplement.

We can, however, mention a few concerns. Algae in general are rich in iodine, posing a risk of irritating the pores and triggering inflammation when consumed in large quantities (beyond 1.1 mg per day). However, the green algae found in dietary supplements are often freshwater algae like chlorella.

These only contain about 0.02 to 0.07%. Green algae capsules contain approximately 250 mg of algae, so the iodine content would be about 0.05 mg per capsule. Considering that the recommended daily dose of iodine for an adult is 150 mg, the content of green algae dietary supplements remains well below the limits and should not present any particular concerns.

Caution however to those intolerant to iodine. Discuss it with your doctor if this is your case.

Another point to consider is that chlorella could potentially cause photosensitization risks when taken orally. This is a hypersensitivity to sunlight that manifests as skin redness or itching, for example. Studies have identified the photosensitizing agent in chlorella as being the pheophorbide-a.

Pheophorbides are formed from the degradation of chlorophyll by chlorophyllase, naturally contained in chlorella. It allows certain wavelengths of visible light to penetrate the skin to the dermal blood vessels and cause vessel damage. However, photosensitive reactions are very rare.

It is important to use the green algae correctly to fully benefit from its properties. When applying it topically, make sure to follow the instructions provided with skincare products containing green algae. Although its use typically does not pose any specific issues, you can perform a skin test by applying the product containing green algae to the inside of your elbow, the inside of your wrist, or behind your ear, for example, to observe any potential skin reactions.

If you consume it, due to its potential photosensitizing effect, protect yourself from the sun by using a sunscreen with a minimum SPF 30 and avoid using products that weaken the skin. Additionally, avoid its intake if you are intolerant to iodine or allergic to mold. If you are taking warfarin, it is advised to be cautious and discuss it with your doctor.

Indeed, dietary supplements containing chlorella are rich in Vitamin K, which the body uses to facilitate blood clotting. Consequently, individuals undergoing blood-thinning treatments, such as warfarin, should refrain from taking this type of product. The information regarding its oral intake by pregnant and breastfeeding women is too limited to make any assertions.

If you notice any side effects, or if you have any doubts, consult your doctor.

• HIDANO A. & al. Chlorella photosensitization : New phytophotodermatosis. International Journal of Dermatology (1984).

• Complément alimentaire : Chlorella. VIDAL (2014).

• MAKPOL S. & al. Toxicity study of Chlorella vulgaris water extract on female Sprague Dawley rats by using the Organization for Economic Cooperation and Development (OECD) Guideline 420. Journal of Applied Phycology (2020).

• NAYARANAN V. Holistic skin care and selection of skin care products in acne. Archives of Clinical & Experimental Dermatology (2020).

• CHAUHAN M. K. & al. Assessment of the toxicological profile of Chlorella (C. vulgaris) powder by performing acute and sub-acute oral toxicity studies in mice. Journal of Applied Phycology (2021).