When is it advised for a client to avoid tanning?

Clients should avoid tanning if they have sunburn or a skin condition due to potential harm to their skin. Sunburn indicates that the skin is already damaged and sensitive; tanning in this state can worsen the damage and lead to longer healing times or complications. Additionally, certain skin conditions can be exacerbated by UV exposure, leading to irritation or flare-ups. Protecting the skin's health is paramount, and advising clients to postpone tanning until their skin is in better condition is crucial for their safety and overall skincare.

The other scenarios presented do not pose the same immediate risks to skin health that sunburn or existing skin conditions do. A recent haircut, plans to go to the beach, or wearing makeup do not inherently increase the risk of adverse skin reactions when tanning.