Strong allergic reaction to poison oak - help!

oatmeal bath
calamine lotion
COLD or cool water.  Hot water is the worst.
He needs to not scratch -- which is hard.
Doctor can prescribe steroid creams.  Check with doctor about taking OTC antihistamines line Benadryl. 

Oh poor guy! So sorry to hear this. (By the way, in California it's Poison Oak, not Ivy - google it and familiarize yourself with how it looks, because it's everywhere and particularly virulent in Fall, when the leaves turn red and shiny and oily.) I'd take him to his pediatrician or Urgent Care, because with an extensive rash like that, he will almost certainly need systemic steroids (oral prednisone) to calm down the reaction he's having. Be especially careful with the eyes/eyelids. And no more hot showers! Cool to cold, if he can stand it (heat will spread the rash) and no regular lotion - only topical steroid cream like hydrocortisone. Ugh, it's the worst. Good luck and get him to a care provider asap. 

This happened to my spouse. The only thing that worked was a cortisone shot from the doctor. I’d recommend checking w your sons pediatrician. 

Sounds like it's systemic and he would benefit from steroids. My son got a very bad case of poison oak last year and the steroids calmed it down very quickly. One note is that the liquid suspension tasted TERRIBLE and there was nothing we could do to get him to take it. We ended up going back to the pharmacy to get pills and that was the day he learned to swallow pills! He was six and we practiced with tiny candies until he got it. For the future, highly recommend washing with tecnu after hiking especially now that you know he's sensitive. We all take tecnu showers after hiking if we think there's any chance we got exposed.

That sounds pretty bad. You probably want to take him to the doctor as it sounds like he is severely allergic. We used Zanfel cream for our landscapers at my previous job. Very important to follow activation and application instructions. Not sure about your sons age so check the label. Good luck! 

Go see a doctor! He may need a steroid shot or something. For now, calamine, cool showers. 

I too and allergic to poison oak/ivy. 
calamine lotion should help. 
do not bathe in hot water. Cool or lukewarm helps. Or an Oatmeal bath. 
 

depending on how bad it is, you may also go to the hospital and get an IV. I once got poison oak in my bloodstream and had to get an IV. Although, the medical staff said it was the worst case of poison oak they’d seen. 

What you can do right now - anti-itch creams like hydrocortisone and icing the most itchy areas. If the area is numb from ice it will not itch. What to do next - get an appointment with a doctor. When I had really bad poison oak a few years ago, I needed to go on steroids in order to get relief. It was really rough. Sorry you are dealing with this, I also took a hot shower after exposure, not knowing I was exposed, and that spreads it to more areas as your pores are open.

Poison oak, in my experience can take many weeks to go away and can even appear to spread (delayed reaction). If they are really uncomfortable - see a doctor.

Speaking from personal experience, if the reaction is very severe you may need to get a prescription for a steroid cream - I had one case of poison oak so bad (I was a poison oak newbie and had also spread it all over by taking hot showers) I ended up in the ER and the cream solved it very quickly when nothing else would. If his eyes are affected, I would definitely see a doctor. For lighter cases, I wash with Tecnu to remove the oil and then treat topically with tea tree oil, which helps dry out the rash and relieve itching, as well as having some antiseptic properties.

Cortisol Steroids from your doctor at this point are likely needed. In the future get Technu. Remove all clothes and bedding and wash thoroughly. Use Technu as directed. It’s a miracle! So sorry! 

Agree with previous posters on 2 counts- 1) it's likely systemic at this point and 2) hot water should be avoided as will irritate the rash.

Once it's systemic it will keep recurring even when seems it's abated.  The only thing that will help is a course of a steroid like prednisone.  And Aveeno oatmeal baths can calm the itching.  Make sure he is always using clean towels and keep sheets changed, clothes washed until the reaction settles down. Especially since he's got around his eye area- really should be on a steroid ASAP.

The oils (urishiol) from the poison oak are what causes the rash, it usually appears 24-48 hours after exposure. Washing with techu after exposure to get those oils off is the best thing for prevention, but once the rash has appeared, I actually think a hot shower (as hot as you can stand it), with the water directed right on the rash is the best way to relieve itching. The way I understand it, the hot water releases histamines that cause the itching, and it usually gives me 6-12 hours of relief. The hot water is not going to cause the rash if the oils have already been removed from your body. If the rash continues to appear in new places on the body, it's systemic and a course of prednisone is warranted. I had a 10 day course of prednisone for a bad case this spring, it worked really well and very quickly. Good luck.

Just want to comment on the misinformation included in a few of the replies in regards to hot water spreading the rash around. Biologically that is not how things work. Once the oil has penetrated your skin and a chemical bond is formed between the oil and your skin cells your fate is sealed and “opening your pores” is not going to do anything for better or for worse. It only seems to spread because there is a delayed reaction to urushiol related to skin thickness and rate of absorption; the resin was already there. Hot versus cold shower effects are all about blood vessel dilation versus constriction and their effect on pain/irritation. 

My husband and I both got very awful cases of poison oak rash one winter from digging in the dirt and unwittingly pulling out roots of the dormant plants, so we never even got the chance to wash off the urushiol. Even the feeling of a cozily heated room was torturous. 
In regards to actually potentially spreading the rash oneself all I have to say is: clean beneath your fingernails.