There are a lot of different IPLs on the market now so I can’t claim to have looked at them all but……. most systems use gel on the skin between the crystal and the skin. It’s hard to know without knowing exactly which system was used.
Most people don’t have that much swelling but some people who are very red or have a lot of brown spots really absorb a lot of light and swell, especially that first treatment. Please be sure and call your dermatologist or laser provider and let her/him know what happened.
There are also rare people who tend to be “allergy prone” types who swell a lot temporarily, even with moderate pressure or other stimuli on the skin. Look up dermatographism. It might apply. Please see your dermatologist if it persists more than a few days. Hope this helps. Dr. I