| Symptoms |
Acute |
Stinging, smarting ⇛
itching |
Itching ⇛
pain |
|
Chronic |
Itching/pain |
Itching/pain |
| Lesions |
Acute |
Erythema ⇛ vesicle ⇛
erosion ⇛ crust ⇛ scaling |
Erythema
⇛ papules ⇛ vesicles ⇛ erosions ⇛ crust ⇛ scaling |
|
Chronic |
Papules, plaques,
fissures, scaling, crusts |
Papules, plaques,
scaling, crusts |
| Margination and site |
Acute |
Sharp, strictly
confined to site of exposure |
Sharp, confined to site
of exposure but spreading in the periphery; usually tiny papules; may become
generalized |
|
Chronic |
Ill-defined |
Ill-defined,
spreads |
| Evolution |
Acute |
Rapid (few hours
after exposure) |
Not so rapid (12
to 72 h after exposure) |
|
Chronic |
Months to years of
repeated exposure |
Months or longer;
exacerbation after every reexposure |
| Causative agents |
|
Dependent on
concentration of agent and state of skin barrier; occurs only above threshold
level |
Relatively independent
of amount applied, usually very low concentrations sufficient but depends on
degree of sensitization |
| Incidence |
|
May occur in
practically everyone |
Occurs only in the
sensitized |