Henna-indigo allergy

I just dyed my hair with the henna-indigo mix two weeks ago and a few days ago, I developed a sever scalp itch and burn.  Today, I discovered a lump (the size of a nickel by the hairline between the nape of my neck and my right ear.  I’m guessing it’s a swollen lymph nodes due to the allergic reaction I’m having, my body is fighting whatever that’s invading my body. 

A little history, I’ve been commercially dye free in the past 5 years and this is the first time I have tried henna-indigo dye.  I did a patch test on my arm but wasnt sensitive before applying the dye to my hair. 

I thought henna was supposed to be all natural and dye free?  The raved reviews got me jumping on the henna band wagon.  And I bought my henna from Down To Earth.  The package ingredients only include powder from Lawsonoa Inermis and Indigofera plant, 100%  natural and pure, no chemical, no pod, no peroxide. 

Has anyone had an allergic reaction after using henna or a mixture of henna and indigo?  What can you do to get rid off the itchiness? 

I’ve made an appointment to go see a dermatologist later this week.