John Found Dip. Chem., C. Chem., MRACI, MAICD
UV induced skin disease will affect all of us in some way as we age. Protecting our skin from ultraviolet light has become an essential part of caring for ourselves. Sunscreens have become one of the most widely used personal care products. Despite our individual preference for skin care almost all of us need to use sunscreens when spending protracted periods outdoors.
Why do we need sun protection?
Solar induced skin disease usually has an exceptionally long latency period. What this means is that your accidental sunburn case today will, in all probability, not show any serious consequences for between 10 and 40 years. Australians are aware more than any other nationalities of the sometimes devastating effects unprotected sun exposure has. Interestingly malignant melanoma was relatively rare in Northern Europe until the 1980’s. It was not until studies showed that the 1960s post war rise in living standards resulted in the population seeking holidays in warmer climates. This eventually led to increased melanoma cases 2 or 3 decades later.
It would not be hard to predict that the recent sudden increase in Chinese wealth will result in the same demographic shift decades from now. The long latency period for skin disease dictates that solar protection from early childhood is a crucial prevention strategy.
What goes into a sunscreen?
The primary purpose of sunscreens is to protect the skin from damaging ultraviolet rays. This can be achieved by adding a combination of chemicals to a lotion or cream which reduce the amount of UV light reaching the skin. Ultraviolet light is arbitrarily broken into “bands” of light wavelengths called UVA, UVB and UVC.
The shorter wavelength and more damaging UVC radiation is largely filtered out by our atmosphere before it reaches the Earth, so it does not pose much of a threat to humans. UVA and B, however, both contribute to long term skin damage so it is important that a sunscreen filters both UVA and UVB known technically as “broad spectrum”. Formulators achieve this by selecting a combination of ingredients that have strong screening effects in both bands. The creative part of formulating is to finish with a stable product that offers both strong efficacy, good coverage and cosmetic elegance.
How are sunscreens tested?
A novel sunscreen must pass many mandatory testing routines to ensure each product is safe and effective. Once a product has been formulated it must be tested to ensure that it will perform for the term of its expiry period. Each product is stored at its maximum storage temperature and humidity for the term of its shelf life and is tested chemically and physically every 3 months for 3 years to ensure that it meets its original specification. Additionally, at the beginning and end of each stability trial a sample is tested to ensure that its preservative system is still functional. The product is then tested to ensure it will perform to its label claim by testing the SPF value.
SPF values are established by irradiating a group of 10 volunteers with ultraviolet light until the first reddening of the skin occurs. The sunscreen is then applied to the skin and the UV radiation is reapplied until the skin reddens once again. The SPF value is calculated by the relative amount of time it takes for unprotected and protected skin to redden. Therefore, if it takes 10 minutes for unprotected skin to appear red then an SPF50 product should take 500 minutes to achieve the same outcome. The product must then be subjected to a complex instrumental analysis to ensure it offers adequate UVA and UVB protection.
Can I own the formula?
Formulating a good, effective sunscreen is often quite challenging. The limitations of type and quantity of active and excipient ingredients means that one formula is very much like another. The addition of low quantities of hero ingredients and fragrance can characterise a product to make it a little unique. Generally the legal and physical requirements for the product don’t allow for much innovation. Most companies invest a great deal of time and effort into formulating.It is quite common for sunscreen manufacturers to create a suite of generic formulations that can be tailored to individual requirements.
There are lots of benefits for the customer in this strategy. Providing there have only been minor changes to the formulation most of the development data can be shared which saves a considerable cost. For this reason, a particular formulation can have a very high value because it forms the backbone of the manufacturers business. In cases where a product is required to be manufactured offshore, arrangements can be made for commercial-in-confidence technology transfer.