Strict answer: Yes, it can be a sin in Jainism if it involves हिंसा or carelessness, even when there is no sexual desire.

But it is not a sexual sin if you are only touching your body for itching, cleaning, or necessity without lust or attachment.

In Jain Dharma:

• Sexual desire is a separate दोष.
• Touching the body for itching is usually not a grave sin in the sexual sense.
• However, scratching can still create हिंसा, because it may injure living beings on the body or harm the body with attachment or carelessness.

So the strictest Jain answer is:

• Not a sexual sin: yes.
• Completely sinless: no, not always.
• If done with strong intent of lust: then it becomes much worse.
• If done only to relieve itching, with minimal force and awareness: the दोष is very small.

Best Jain conduct: Try to use the least harmful way to relieve itching, with mindfulness and non-attachment.