Not to stand naked before a candle:
One is not to stand before a candle naked as all that stand naked before a candle become crippled. [Nevertheless, in the Poskim we find a number of disclaimers towards this warning: Some explain that this danger only applies when standing still in front of the candle. It is however permitted to walk by the candle, even if one is unclothed. Others write it only applies when one stands in very close proximity to the candle, and not from a distance, even if he is able to benefit from the light. Others rule that this danger only applies towards adults, and not towards children.]
Shabbos candles: It is customary to cover the children [and certainly adults] so they not be naked in front of the [Shabbos] candles due to it being a belittlement of the Mitzvah [Bizuiy Mitzvah]. [This applies even if one is at a distance from the candles, and even if the child is not standing in front of the candles. This applies even if only the Erva is revealed while the remainder of the body remains covered. Thus, one is not to change a baby’s diaper in the same room as the Shabbos candles. The same applies against doing any belittling matter in front of the candles. The same applies to any other Mitzvah candle such as a Havdala candle, Chanukah candles, and candles of a Shul. It however does not apply to a Yartzite or Yizkor candle that is lit at home.]
Does the above danger apply when standing undressed in front of electric light?
It is unclear as to whether the above danger is applicable to electric light.
May one be undressed in a Mikveh or bathhouse in front of candles?
 Admur Shemiras Haguf Vehanefesh 9; Admur 275/13 in parentheses “It is customary to cover the children so they not be naked in front of the [Shabbos] candles due to Bizuiy Mitzvah (and also during the week there is danger to stand before the candles naked).”; Pesachim 112b; Derisha 275/1; Elya Raba 275/14; Beir Heiytiv 275/10; M”B 275/27
Other opinions: Some Poskim rule that in today’s times there is no longer a danger involved in this matter, as the natures have changed since the times of the Talmud. [Tosefes Shabbos 275/16; Teshuros Shaiy 51; Zecher Yehosef 28
 Chikreiy Halachos 1/32
 Roshei Bashmayim 6; Makor Chaim 5; Zecher Yehosef 28; See Yabia Omer Y.D. 3/7
 M”B ibid in name of Elya Raba 275/14
 Admur 275/13; Rama 275/12; Darkei Moshe 275/4; Rokeiach 45
 See Chikreiy Halachos ibid; Piskeiy Teshuvos ibid
 Kaf Hachaim 275/41
 Kaf Hachaim 275/42
 Levush 275; Tosefes Shabbos 275/16
 See Yabia Omer ibid; Doveiv Meisharim 1/124; Piskeiy Teshuvos 275 footnote 38 that perhaps there is no danger when the candle is covered by glass
 Shalmas Chaim Y.D. 33; Meorei Or 15b
 The reason: As whatever is done for the sake of immersion and bathing there is no danger involved. [ibid]
 Piskeiy Teshuvos 276/4