Allergic reaction to Thyroxine medication

Hi Jennyann, despite what is propagated on the internet, artificial thyroxine is identical to the natural hormone T4 produced by the human thyroid. T4 occurs in two form (two enantiomers) levo-T4 and dextro-T4 and only the levo molecule is biologically active as thyroid hormone. 

For this reason, it is more likely that you might be allergic to an inactive substance in your thyroid hormone replacement medication. Did you ever have an allergy test? You could even wet a levo tablet and rub a tiny amount onto your inner arm. Leave it for 48 hours and check if you detect any irritation.  

Having said that you have to make sure that your thyroid hormone levels are ok. Hyperthyroidism and hypothyroidism may cause skin problems. I have Graves disease and was hyperthyroid several times. In my case, being hyper made it more likely to get itchy skin. 

I myself have dry sensitive skin and am allergic to sulfonated fatty acids (found in shampoos, soaps, toothpaste, detergents, dish-washing-liquid). Even if you are not allergic to those is makes sense to use the mildest shampoo, etc that you can source. 

Test have shown that patients with itchy skin have (in general) drier skin compared to a control group. 

"The level of stratum corneum water content was significantly lower in the patients experiencing itching compared to those without the symptom, and it was significantly lower in both patient groups than in the control group. Transepidermal water loss (TEWL) was significantly higher in the patients experiencing itching than those without the symptom, and it was significantly higher in both patient groups than in the control group. For all study participants, relationships between the stratum corneum water content and TEWL against serum zinc were examined. There was a positive correlation between the stratum corneum water content and serum zinc, and a negative correlation was found between TEWL and serum zinc." The paragraph is from "Association between itching and the serum zinc levels in patients with varicose veins", 2017, Journal of Pharmaceutical Healthcare and Sciences. 

You could have your Zinc level checked. It helps me to apply Calamine lotion (a liquid Zinc oxide preparation) and some evidence seems to suggest that Zinc can be absorbed transdermally. You also could have a look at the SeroZinc spray by LaRoche Posay. 

The other thing I would suggest is the regular consumption of probiotic food. I have been eating (home make kefir) for several years and can't imagine going without it. If you need more info regarding kefir I am happy to share more details. 

Btw, probiotics have been shown to have beneficial effects on the flora of the gut and vagina.