Does tecta cause hives? does it prohibit the absorption of nutrients?

Yes. Maybe.: Any medication, food, or even environmental, substances, can cause hives, an allergic reaction. Also, with chronic use there may be some effect on nutrition. Though, not common. Long-term use needs to be monitored by doc. Correct cause, by losing weight, eating more fiber, less fat and protein, smaller meals, and avoiding food triggers. See http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4110863/