She's been complaining for a whole month now. We've tried literally everything: changed her shampoo,…

She's been complaining for a whole month now. We've tried literally everything: changed her shampoo, started washing her hair every day – nothing helps. Actually, it's the opposite; we tried washing it less often – also no use. I've checked her for lice about a hundred times, carefully examining every strand – there are none. Yes, if she had them, my younger one would have them too by now. In a month, they would have multiplied so much that it would be impossible not to notice. She doesn't have dandruff either. Most likely, I'm attributing this to the onset of puberty and the sebaceous glands' activity, but again – her head itches even when it's clean 🙄. Sometimes she scratches so much she makes herself bleed. Yesterday I looked for lice again – found none. Has anyone else experienced this with their kids?