There are a couple of common mistakes that crop up when someone says “My partner is allergic to hemp/jute/whatever rope!”.
The most important is missing the consideration that they may not be allergic to the rope at all.
Chemicals
Mass produced rope is almost always coated with chemicals as lubricant in the manufacturing process. Some ropes are impregnated with chemicals to preserve them and/or stop them rotting in wet conditions. Some of these chemicals are not good for the skin.
Make sure that it’s not these chemicals that you’re reacting to.
Synthetic ropes aren’t made with the same chemicals so it’s easy to say “Hey we had a bad reaction to that fibre but not with synthetic rope” and therefore erroneously conclude it was the fibre when it might be the chemicals coating the fibre.
Hemp / Jute
Hemp and Jute are both bast fibres. Bast is the inner skin of the plant, there are many kinds of bast fibres
Generally for bondage only Jute, Hemp and Flax are in use.
Remember that these ropes although all bast fibre ropes are entirely different species and a reaction to one does not necessarily imply a reaction to another. Try different types of rope if you’re having problems with your first choice and if you’ve definitively isolated the reaction to the fibre and not any other factor.
Any other factor
Irritating shit
New raw, or just plain poor quality rope can be irritating. This can cause redness and rash which can be mistaken for an allergic reaction. Generally irritating the skin isn’t going to cause long term problems unless misinterpreted as an allergic reaction prompting you to use a less than ideal rope for no real reason.
Untreated rope
This is in practice Irritating shit that’s your own fault.
If your rope is very irritating (with the obvious exception of stuff that’s meant to be harsh and irritating like coconut rope for example) you should probably treat it properly even purpose made high quality bondage rope.
It stinks
If the rope stinks of chemicals this is another of the you didn’t really treat your rope properly ones and p.s. maybe think about buying some better rope that’s been made for bondage use.
Conclusion
Real allergies to natural fibres do exist and you might actually have one. However don’t assume you do when there are other factors that might be causing irritation. To really confirm go to a physician with your concern and get an actual allergy test. Without one you may be cutting yourself off from your best rope choice for no good reason.