Allantoin

Soothing and non-irritating to the skin. It stimulates healthy tissue formation and healing of wounds and removes scales and crusts of dead skin cells. According to the FDA, allantoin possesses a softening effect on keratin, the protein abundant in the skin's surface cells, allowing water to be absorbed. 
Allantoin softens and smooths keratin, which is a tough inflexible protein found in the epidermis

Urea

Urea is a moisturizer.

Camphor and Menthol

Mild analgesics (pain relievers). They give No-Crack a cooling effect and help relieve pain and itching.

Mineral oil and Petrolatum

Mineral oil and Petrolatum form a barrier on the surface of the skin. According to the Journal of the American Academy of Dermatology, petrolatum "prevents moisture loss, forms a protective barrier on the skin, penetrates every layer of the stratum corneum, and assists damaged skin to repair itself." They also act as emollients.

Lanolin

Lanolin can soften dry, chapped, or cracked skin. It acts as an emollient (a substance that softens or soothes) and a moisturizer. A small percentage of the population is sensitive/allergic to lanolin.

Natural oil

Natural oil (corn oil) is an emollient. May provide healing ingredients to the skin.