What Causes Deep, Non-healing Skin Fissures On Finger Tips And Feet?

Hello, I am a nurse attempting to find a reason and treatment for my family members condition. She suffers with chronic deep non-healing skin fissures on her finger tips and feet. They are painful and they do not itch, they are mostly dry, do not appear to granulate. She has tried vaseline and antibacterial creams periodically. I haven’t seen her latest one on her foot but she says it has been there for 6 months and has gotten deeper and longer. I have suggested which ever treatments we try to test consistently. Could it be dyshidrosis? Psoriasis? Fungal? I’ve advised everything from stop using the vaseline, stop using the antibacterial, drink more water, wash only with warm water, soap in moderation, pat dry, lotions overnight with gloves/socks. I will take a look at it tomorrow and will probably suggest, a lotion with zinc and dimethicone but what do you think of trying an antifungal? I have also suggested she have some blood work done to check BS, TSH, CBC and vitamin levels. What do you think?