What could these marks be on DS's back?

[Backmarks]

He's 20, had them for years. Sometimes they're hardly noticeable, other times they're very red like in the photo, taken this morning. I used to think they were stretch marks, but they fade over time don't they? I've done a reverse image search but haven't found anything the same.

Stretch marks, both DS have them on back from huge growth spurts in teens. DH also has them

I'd have said stretch marks. Weird that they come and go. Usually fade to a silvery line. Does his weight fluctuate?

They are stretch marks. Both my sons have them but more so my eldest. I'd say he had a big growth spurt at some point.
If you google it will show you. I was horrified at first. It looked like whip marks !

Stretch marks, my DS has them too after he shot up about 4 years ago. I also was a bit worried the first time I saw them!

Another vote for stretchmarks. I have lots on my tummy and sometimes they get very itchy. If I've scratched them they will go red like your pic, otherwise they are very light.

Stretch marks. My brother had them. His has faded to silvery lines now. He is on the broader side

Stretch marks.

Stretch marks / redden up again in response to a bit of gain or pressure and take a while to turn to silver.

Stretch marks. I have them from puberty and from putting on weight in my teens, some faded to silvery but others have stayed red / reddish purple. Totally normal :)

He looks like he has a narrow waist and very broad shoulders, so does he swim or do weights? If so he will probably be reviving them regularly as his muscles build, and that’s why they haven’t just stopped and faded to silver.

Stretchmarks 100%

My youngest DS had them and nothing made them any less red/angry looking.

But like all stretchmarks they went silver over time. He's 21 now and you can hardly see them.

They're stretch marks 100%. Lots of boys have them on their backs due to growth spurts, especially taller boys. All my brothers do and my husband, though they have faded somewhat as they've aged.

They tend to be more pronounced on pale skin, my eldest brother is a pasty ginger like me and his look like he's been mauled by a tiger.

Stretch marks for sure, I remember my little brother getting them when he went through growth spurts as a child, he’s over 6’ as an adult. I never got any but I’m short…

@Backmarks Hi my daughter has ones very much like the ones on your sons back but she gets them on her legs when I took her to the doctors when she was younger I was told they would come and go and it's nothing more than blood being nearer to the surface that causes them (sorry but I can't remember what the actual name is) but was told it's nothing to worry about. Hope that helps and I've made sense explaining xx

Did he have a big growth spurt? My nephew had these as he shot up in height. I also had stretch marks on my thighs/abdomen when pregnant. I used bio oil, and they faded eventually.

DS has these from growing a foot in about a month!
He is conscious of them. They look like he has been whipped.

Yes stretch marks, DD 15 has them from a rapid growth spurt and fluctuating in weight - you can buy creams to help I believe, no idea if they work though

Thanks everyone! I always assumed they were stretch marks but thought I must be wrong as they hadn't faded, and are so very red today.

Neither his height nor weight have changed much in the last few years - he reached his current height fairly quickly about 4 years ago and has always been slim. He does weights on and off, but not much lately.

Both my teen sons have them across their backs
Stretch marks from growing taller I assumed