It's still eczema. Eczema is both plural and singular.
The plural and singular form of eczema remains as 'eczema'. 'Eczma' is a mass noun, thus doesn't really have a plural. E.g 'I have eczma.' 'All my family has eczma'.
There is no plural form. Do and Do not are verbs
The plural form of him, her, or it is them. (objective pronouns)
Bridges is the plural form of bridge.
The plural form of "is" is "are."
The plural form of "I" is "we."
The plural form of "was" is "were."
"Groceries" is the plural form of "grocery."
"Beliefs" does not have a plural form, as it is already plural. Beliefs is the plural form of belief.
The plural form of mouth is mouths. The plural form of month is months. The Mounth is a range of hills in Scotland and does not have a plural form.
The plural form of the demonstrative pronoun 'that' is those.
The plural form is metres.