Broad spectrum of good options already listed. I used to be highly reactive - go to the hospital reactive (western medicine thinking would call that allergic). I found a method of clearing "allergies" called NAET, Nambudribauds Allergy Elimination Technique. Now I can be around it some and touch it a little and just get modest itching etc.
If I'm going to climb through it in a tree I pre-coat my exposed skin with Tecnu, wear a Tyvec suit, limit time as much as possible, post wash with Tecnu on the job, home to shower as efficiently as possible, wash exposed areas with Tecnu Extreme (has oil absorbing capsules in it and is $9 per tube), then rewash exposed areas with Zanfel ($35 a tube but highly effective oil absorbing capsules in it). Usually would get little or no reaction. Keep Zanfel in the truck in case I feel any follow on itching the next day(s) or if I get issues from transfer of oils from my gear.