Another characteristic of the allergic contact dermatitis rash is that it usually appears after a day or two after exposure to the allergen, unlike irritant contact dermatitis that appears immediately after the contact with the trigger. Other symptoms may include itching, skin redness or inflammation, localized swelling and the area may become more tender or warmer. If left untreated, the skin may darken and become leathery and cracked. Pain can also be present. Dermatitis can occur anywhere on the skin, but is most common on the hands (22% of people), scattered across the body (18%), or on the face (17%).The rash and other symptoms typically occur 24 to 48 hours after the exposure; in some cases, the rash may persist for weeks. Once an individual has developed a skin reaction to a certain substance it is most likely that they will have it for the rest of their life, and the symptoms will reappear when in contact with the allergen. Cause
Common allergens implicated include the following: 

Bacitracin – topical antibiotic found by itself, or as Polysporin or Triple Antibiotic
Balsam of Peru (Myroxylon pereirae) – used in food and drink for flavoring, in perfumes and toiletries for fragrance, and in medicine and pharmaceutical items for healing properties; derived from tree resin. It may also be a component of artificial vanilla and/or cinnamon flavorings. Chromium – used in the tanning of leather. Also a component of uncured cement/mortar, facial cosmetics and some bar soaps.
Gunther disease is a congenital form of erythropoietic porphyria. The word porphyria originated from the Greek word porphura. Porphura actually means "purple pigment", which, in suggestion, the color that the body fluid changes when a person has Gunthers disease. It is a rare, autosomal recessive metabolic disorder affecting heme, caused by deficiency of the enzyme uroporphyrinogen cosynthetase. It is extremely rare, with a prevalence estimated at 1 in 1,000,000 or less. There have been times that prior to birth of a fetus, Gunthers disease has been shown to lead to anemia. In milder cases patients have not presented any symptoms until they have reached adulthood. In Gunthers disease, porphyrins are accumulated in the teeth and bones and an increased amount are seen in the plasma, bone marrow, feces, red blood cells, and urine. Symptoms and signs
Though expressivity is varied depending on the mutation responsible for decrease in enzyme function, severe cutaneous sensitivity is present in most cases of this Porphyria. An estimated 30–40% of cases are due to the C73R mutation, which decreases stability of the enzyme and results in <1% of its activity. Exposure to long-wave ultraviolet light causes the affected skin to thicken and produce vesicles that are prone to rupture and infection; these secondary infections, along with bone resorption, can lead to disfigurement of the sun-exposed face and extremities. Enzyme dysfunction prevents the normal production of heme and hemolytic anemia is another common symptom, though a lack of hemolysis in this disease is possible.