Question:

Which is better for covering up on a sunny day, light or dark clothes?

Answer from Express Scripts Canada Pharmacist, Syed Khalid:

For most of us, the accepted wisdom is that it’s best to wear white on a hot sunny day, since white reflects the sun’s heat, leaving us feeling cooler. But the answer to this question is perhaps a little more complicated than that.

Yes, white clothing is the most effective at repelling heat, but this is not the only thing to keep in mind.

You should also think about fit.

• Wearing a loose fitting garment in a light breeze produces a kind of convection current as hot air escapes the top of your clothing and refreshing cool air flows in from the bottom. This air flow further enhances the cooling effect by increasing the rate at which your perspiration evaporates.

But keeping cool isn't the only thing to bear in mind when choosing the colour of your summer wardrobe.

More importantly, the colour of your clothing has a significant impact on your skin's exposure to UV rays.

• Brighter and darker colours such as red, black and navy blue absorb more UV rays than lighter colours like white, yellow and pink. The more intense the shade, the better protection the clothing provides. The typical white cotton T-shirt has a UPF – ultraviolet protection factor –rating of just 5, while a dark green cotton shirt can have a UPF rating of more than 10. The higher the UPF rating, the better it is at reflecting harmful UV rays.

In the end, the choice of material is perhaps a more important consideration than colour. While natural light-weight fabrics like cotton and silk may seem more comfortable on a hot sunny day, synthetic fibers such as polyester and rayon are best at blocking harmful UV rays, as are wool, denim and corduroy.

Tight fitting clothing lets more UV rays through the fabric. Also, if fabrics stretch or get wet, that reduces their effectiveness in protecting you from the sun. Some brands of clothing are now available that are specially made to provide sun protection and come with UPF ratings.

So, while it doesn't make a huge difference whether you’re wearing light or dark clothes in terms of how cool you will feel, it’s important to make sure your clothes are loose fitting, as this is a major factor in both keeping cool and blocking harmful UV rays. The most important thing to remember is that no single type of sun protection is good enough on its own.

The use of:

• sunscreen,
• hats,
• sunglasses, and
• shade

must go together with your choice of summer fashion for all around safety from the harmful effects of the sun.

So keep loose, stay cool, lean towards darker, brighter colours, and don’t forget the sunscreen! Above all, enjoy those warm sunny days!

Until next time, I’m Syed Khalid, and this has been Ask the Pharmacist. I wish you good health.