Some people mistake impetigo or other itchy skin infections for bad eczema, some people scratch their eczema patches or dermatitis or heat-rash until it breaks the skin, allowing infection to set in and prevent healing. An anti-microbial soap - which pine-tar can be - can assist with healing infections that tend to come secondary to constant itching and irritation.
Soaps and lotions with drying properties can dry up crusty, weepy areas of raw skin that can be infection-prone and allow them to more easily dry up and scab over.
Nothing can 'cure' eczema -- it's a genetic autoimmune disorder where the body reacts mistakenly to perceived irritants.
You can reduce the impact it has on you by keeping your immune system healthy, using appropriate treatments for bad flare-ups to reduce inflammation and immune response, avoiding known allergies and triggers, which are different for every individual -- thus no 'one-size-fits-all' remedies -- and by keeping irritated areas clean, dry, and moisturized, and if a rash lasts in one spot more than a few days at a time, make sure it's not infected.
I'm not gonna say what my doc always told me about 'try not to itch' because that's just impossible lol. But try not to itch enough to break the skin or make it raw.
Both the antimicrobial and drying properties are what help horses with hoof-rot or fungal infections in their feet. We used to clean em with a spray-bottle with a dilute solution of bleach, then paint with the pine-tar once they dried. Somehow I don't think that particular method will work on the back of my knee or the crease of my elbow.
BTW -- many people with eczema or asthma must avoid milk, it's very good at triggering allergies, as well as excess mucous production. The milk protien passes too easily through the digestive tract into the bloodstream without being fully digested, because, well... we're humans, not baby cows lol. And we don't make all the enzymes as adults that babies make in order to properly digest milk. That's why it irritates the intestines, and triggers allergies when it gets in the bloodstream.