Bright red spot after crust fell off from Pulsed Dye Laser. How long will this take to go away?

I would treat the area with a light IPL Limelight treatment to help reduce the redness caused by the laser session. Best, Dr. KaramanoukianLos Angeles

It can take 1-2 weeks to resolve. If it doesn't, I suggest speaking to your physician for skin care and possible other laser treatment.  Best, Dr. Emer.

Pulsed dye lasers are great for pink or red skin or PIE.

Efficacy from pulsed dye lasers is related to destruction of blood vessels with expected bruising and unfortunately, potential for hyperpigmentation, hence the need to use such products. Link is provided for more information.
Pulsed dye laser can cause bruising and swelling and I precondition and treat my patients with a bioflavonoid product called Swell-x pt (post treatment) and also an oral supplement for PIH relief called Scler-X and I find them to be effective. 
For hyperpigmentation relief we use a HQ and non HQ based creams in  the U.S. called Melarase.
Hratch L Karamanoukian MD FACS

Depends on your skin type, location and sun exposure. Ensure you protect using a high factor SPF sunscreen. It can take several weeks before fading. All the best, Dr Davin Lim. Brisbane. Australia.