DNCB is a chemical used to develop colour photographs. Some PHAs use a very dilute solution to enhance immune system function. DNCB is absorbed through the skin and carried to the lymph nodes by immune system cells. Within the lymph node network, the chemical is used to stimulate several parts of the immune system, both to produce chemicals that regulate the immune system and to increase specific immune cell levels. DNCB is used to stabilize CD4+ cell levels (or at least slow their decline) and increase levels of other immune cells important in the control of HIV. Several small trials support these claims, including a Brazilian trial of 35 individuals who used DNCB over an 18-month period. The PHAs in this study experienced increases in CD4+ and other immune cells. They also experienced significant weight gain compared with a control group that did not use DNCB. No one in this trial had access to antiretroviral therapy.

DNCB is usually applied in a diluted solution to a small patch of skin in decreasing doses over time, as the immune system becomes more responsive. Applying DNCB should produce redness, itchiness and perhaps even blisters or raised welts. These reactions are all signs that the immune system is responding. If the symptoms are too severe, a person usually switches to a more dilute dose. If there are no visible symptoms, a person may use a more concentrated solution. For most people, DNCB seems to have few side effects beyond the itching and discomfort where the chemical is applied. These symptoms can be treated with calamine lotion or other over-the-counter anti-itch creams. A small percentage of people have a severe reaction to DNCB and must discontinue use. DNCB can also make the spot on which it is applied more sensitive to the sun. A DNCB starter kit costs about $50 (US). DNCB is not regulated nor available in Canada.