How long after microneedling treatment (.5mm) can I use *chemical* sunscreen?

Hello there, 
      I would STRONGLY recommend a good physical sunblock, as the long-term effects of chemical sunscreen is not known. That being said, the microneedling injuries should be closed and healed within 24 hours. I would wait another day or so after this since the skin will be more sensitive. You can always try applying a small amount in a test area to make sure you do not get any type of reaction. Hope this helps. 
Sarah RN BSN 

Thank you for your question. I understand your concerns with physical versus chemical sunscreen from a financial standpoint but as far its effects on the skin physical sunscreen is far safer. Keep in mind that you are investing in your skin by spending money on in office procedures and it is just as important if not more important to use the proper skincare products including sunscreen for optimal results from your procedures as well as long term care of the skin.
With that being said, each provider microneedling protocol is different. I like the immediate use of sunscreen but holding off for 72 hours for all other products including makeup in order to allow your skin to heal and prevent breakouts, as well by clogging the pores the procedure creates. If you must use chemical sunscreen, wait 72 hours to do so and make sure to follow up with your provider, as well to ensure you are  healing properly.

Every provider will have slightly different protocols following your microneedling treatment, so it’s best to ask him or her for specific guidelines. You have to be careful about what you put on your skin directly after microneedling, as the microchannels that it creates allows for increased absorption. This is why physical sunscreens are recommended versus chemical SPFs. Physical sunscreens like hats and long clothing are not absorbed into your skin, while chemical sunscreens are. There are now a variety of clear mineral-based sunscreens that don’t leave a white film on your skin.

This is a great question. I would wait at least 24 hours before applying any sunscreen. Microneedling creates microbial wounds in the skin to help self healing of the skin and reproduce collagen, its very important to keep the skin clean and fresh after the treatment.
LOVA- Lake Oswego Vein & Aesthetic 

Hi, I do not recommend putting on sunscreen for the first 24 hours after microneedling.  Wear a hat, and avoid the sun.  Use what is directed.  After the 24 hours, I'd recommend mineral sunscreen (Avene makes a great one that's reasonably priced).  After 3 days, you can go back to using your chemical sunscreen.Best,Dr. Huo

I would wait at least 12 hours before putting any sunscreen on. I wouldn’t put any sunscreen on directly after a microneedle, chemical or physical, the molecule size of the sunscreen can actually make it more likely for you to breakout after. It also makes it more difficult for other products to enter the channels you created after the microneedle such as growth factors. If it is chemical it obviously could cause more irritation. 

I would wait at least 24 hours before putting on sunscreen after microneedling.   It is best to avoid the sun, if possible for a few days following the procedure.  I would not plan a trip to the beach following the procedure for a few days.