This question was actually asked by my 15-year-old niece, who stayed with us for a week on vacation. And it was prompted by a bad sunburn.
Long story short: our pool is open now, and the weather was beautiful. So we spent a it f time at the pool. Now, we weren’t stupid about it – my whole family is fish belly white, so we slathered on SPF 100 sunscreen that I selected for being water resistant. Sadly, I missed the fact that it needed to be reapplied every 80 minutes when in water.
We all burnt, and since my son was in the pool longest he burnt worst. And two days later he developed a blister on his shoulder. So, while we’re taking care of it, my niece asks “what made his skin bubble up?”
At that moment, I’m afraid my answer was “you’re not helping!” But it’s a good question.
To start with, let’s talk about sunburns. And I’ll be honest here: I always assumed that sunburn happened because of heat. I’ve only sunburned in the late spring and summer, after all, which is when the weather is hot. But according to What happens when you get a sunburn?, an article from Scientific American, the heat of the sun’s rays has nothing to do with it:
A sunburn manifested by cutaneous redness, swelling and painis an acute toxic reaction caused by exposure to the sun’s ultraviolet radiation. Although the precise mechanism by which a sunburn occurs has not been clearly identified, complex chemical reactions and pathways take place that most likely result in the clinical symptoms.
I probably should have realized this, given how much time and energy is put into talking about how sunscreen protects from UV light. But it just never sank in.
The article (which is short, and I recommend that you read it) goes on to explain that the redness and swelling from a sunburn appears to be caused by ultraviolet radiation damaging DNA in your skin. This causes your skin to syntesize different proteins and enzymes, which results in dilated blood vessels and inflammation, which causes redness, swelling, and pain. It can also utterly destroy skin cells, which is why you peel if you get a bad sunburn.
The heat of the sunlight also has nothing to do with why sunburns feel warm to the touch. That’s caused by the dialated vlood vessels. This causes increased blood flow, which raises the skin temperature slightly in the burned area.
What is a blister?
You’ve probably had one. If you haven’t, then it is a fluid-filled bubble on your skin. This fluid can be:
1. Serum, which is the clear fluid your blood cells float in.
2. Blood plasma, which is serum plus the clotting proteins in blood (called fibrinogen.
4. Pus (which is a sign the blister is infected).
When a blister forms, it is (usually) a sign that the body is trying to heal itself. The fluid acts as a cushion for the tissue beneath the blister, serving to protect it from further damage as it heals.
The word blister appears to derive from the Middle Dutch blyster “swelling”, which may come from the proto-Indo-European word *bhlei- “to blow, swell”. This is debated, however, because it could also derive from the Old French blestre “blister, lump, bump”, which could come from the Old Norse blastr “a blowing”.
How does a sunburn cause a blister?
In truth, all burns can cause blisters. First degree burns my develop blisters hours or days after the burn is initially suffered, while second degree burns will develop them immediately. In either case, the body is attempting to protect itself from further harm or infection while it heals. Sunburns are no exception to this rule.
Caring for blisters
Both WebMD and the Mayo Clinic recommend that, if the blister isn’t significantly painful and if it doesn’t prevent you from walking or using your hands, then you are better off leaving it alone. If you absolutly have to drain it, here’s what you should do:
- Wash your hands and the blister with soap and warm water.
- Swab the blister with iodine.
- Sterilize a clean, sharp needle by wiping it with rubbing alcohol.
- Use the needle to puncture the blister.
- Let the fluid drain, but leave the overlying skin in place. (If the fluid is any color but clear, seek medical attention.)
- Apply an ointment (petroleum jelly will work, but an antibiotic ointment or cream is better) to the blister, and cover it with a nonstick gauze bandage.
- Change the dressing and apply more ointment daily.
- Watch for signs of infection, such as pus or drainage, as the blister heals.
Yeah. Remember how I mentioned that, up at the top? The body can repair damage to DNA over time. But, if you overwhelm that self-repair mechanism through repeated excessive exposure to ultraviolet radiation, the damaged DNA can lead to the development of skin cancer. So, seriously, use a good sunscreen. SPF 30 or higher. And be sure you read the instructions!