HET-CAM: alternative non-animal test for assessing eye irritation
The HET-CAM (Hen's Egg Test – Chorioallantoic Membrane) is now the gold standard method for assessing the irritant potential of a cosmetic product on the eyes without resorting to animal testing. In accordance with European (Regulation EC 1223/2009) and Swiss (OCos/OSAV) requirements, this test uses the chorioallantoic membrane of an incubated chicken egg: an ultra-thin membrane that is highly vascularized and extremely sensitive to chemical irritants.
Test principle
- Incubation of the egg – The egg is incubated for 9 to 10 days at 37°C, at which point the chorioallantoic membrane is fully developed.
- Product application – A small drop (10 µL) of the cosmetic product to be tested is placed directly on the membrane.
- Marking lesions – Specific dyes (usually phenol sulfonate red) are added to highlight vascular changes: redness, microcoagulations, hemorrhages, or vessel rupture.
- Observation and scoring – The membrane is observed for 5 minutes, then again after 30 minutes. The extent and speed of vascular changes are noted according to a standardized scoring table (0 = no irritation, 5 = severe irritation).
Benefits of HET-CAM
- Absence of mature animals : the method uses an embryo, which classifies it as a 3R (Replacement) technique.
- High sensitivity : even mild irritants cause visible vascular responses, allowing for detailed classification according to the GHS system.
- Quickly executable : The entire protocol takes less than an hour, ideal for development phases where time is of the essence.
- Reduced cost : no need for expensive equipment or animal maintenance, making the test economically attractive for R&D laboratories.
Limitations to be aware of
- No corneal permeability measurement Unlike BCOP or reconstituted corneal models, HET-CAM does not provide direct information on the penetration of the product into the cornea.
- Semi-quantitative interpretation : scoring is based on visual observation, which can introduce inter-operator variability if the criteria are not strictly harmonized.
- Applicability to highly lipophilic formulations : thick oils may not spread evenly over the membrane, sometimes requiring the addition of a compatible solvent.
Inclusion in the regulatory file
The HET-CAM results are incorporated into the DIP/PIF (Product Information File) and are used to justify the product's eye irritation classification. They are particularly relevant for eye creams, mascaras, eye makeup removers and any other product that may come into contact with the eye area.
By combining HET-CAM with other in vitro tests (BCOP, RhCE) to cover corneal permeability, manufacturers obtain a complete dossier that complies with Swiss, European, and UK requirements. This holistic approach reinforces the scientific credibility of the product, speeds up the process of obtaining a notification number, and reassures consumers about the safety of their eye care products.